SPAM 150 CApplication examples

Technical information

2

1MRS 751841-MTI EN

Issued 2000-06-22Modified 2003-04-01Version B (replaces 350 SPAM 04 EN1)Checked HSApproved MÖ

Data subject to change without notice

Application examples forthe relay SPAM 150 C

Contents Introduction ................................................................................................................... 2General about the protective functions ........................................................................... 3Some notes and useful hints ............................................................................................ 4

Connection with two phase current transformers ...................................................... 4Stabilizing for virtual earth-fault currents .................................................................. 4Problems with false E/F or U/B trips during start-up ................................................ 4Increasing the sensitivity of the earth-fault protection ............................................... 4Optimizing the needed time left to restart ................................................................. 4Time constant versus safe stall time t6x ...................................................................... 4External trip via control input ................................................................................... 5Disabling of restart inhibit for use outside SPAM 150 C ........................................... 5Mutual restart inhibit for multimotor applications .................................................... 5Note about the contactor versus circuit-breaker drives ............................................... 5

Example 1. Protecting a circuit breaker controlled motor in an isolated network. ........... 6Example 2. Determining suitable setting values for a standard,

contactor controlled direct started motor ..................................................... 9Example 3. Protecting a direct started motor with a low safe stall time ......................... 11Example 4. Protecting of a feeder cable, a transformer or another non-rotating object .... 12

The parameter p of the thermal unit........................................................................ 13Example 5. How to use the start-up time counter ........................................................ 15Example 6. How to set the phase unbalance and phase reversal unit ............................. 16Appendixies .................................................................................................................. 17

Introduction The motor protection relay SPAM 150 C is aversatile multifunction relay, mainly designedfor protection of standard a.c. motors in a widerange of motor applications. Due to the largenumber of protective functions integrated, therelay provides a complete protection againstmotor damage caused by electrical faults.

The relay can also be applied on other objectscalling for a thermal overload protection suchas feeder cables and power transformers.

3

General aboutthe protectivefunctions

The thermal overload unit of the relay protectsthe motor against both short-time and long timeoverloading. The highest permissible continu-ous load is defined by the relay setting Iθ. Nor-mally the setting equals the rated full load cur-rent of the motor at 40°C ambient. Under theabove conditions a 5% increase in the motorcurrent will cause the thermal unit to operateafter an infinite period of time. If the ambienttemperature of the motor is constantly below40°C, the setting Iθ can be chosen to be 1.05...1.10 times the motor full load current (FLC).

Overload conditions of short duration occurmainly during motor start-ups. Normally twostarts from a cold condition and one start froma hot condition are permitted. Thus the settingt6x, which defines the characteristic of the ther-mal unit, is worked out according to the start-ing time of the motor. The setting can easily bedefined by means of the hot curve time/currentdiagram. The t6x curve allowing the starting cur-rent for the start-up time (plus a margin) is se-lected. Using the same t6x curve in the cold curvediagram, the total starting time can be read out,referring to a cold motor condition. As a ruleof thumb, a setting of t6x ≈ 1.6...2.0 times themotor start-up time generally gives the wantedtwo cold/one hot start-up behaviour.

The prior alarm from the thermal unit can beused to avoid unnecessary tripping due to a be-ginning thermal overload. When the prior alarmcontact operates, the load of the motor can bereduced to avoid a trip. The level of the prioralarm can separately be set in per cent of thethermal trip level. The prior alarm level canthus be set to a suitable level, which makes itpossible to use the motor to its full thermal ca-pacity without causing a trip due to long-timeoverloading.

The thermal stress during any single start-upcondition is monitored by the start-up supervi-sion, which is normally used to monitor thethermal stress equvivalent product I2 x t. An-other possibility is also to use the relay unit as adefinite time overcurrent monitor. The latter inparticular is used with non-motor applications.

Regardless of which function mode is used, theexternal input to the relay can be programmedto link an external trip inhibit order e.g. from aspeed switch on the motor shaft to make a dis-tinction between a jammed motor condition ora start-up condition.

The high-set overcurrent unit constitutes aninterwinding short-circuit protection for themotor and a phase-to-phase short-circuit pro-tection for the feeder cable. The current settingis automatically doubled during start-up. Thusthe current setting can be given a value lowerthan the motor starting current. Normally thesetting can be chosen to 0.75 times the motorstarting current. With a suitable operating timeset, this feature will enable the high-set over-current unit to operate, if the motor is jammedwhile the motor is running.

When the relay is used for protection of con-tactor-controlled motors, the high-set overcur-rent unit is set out of operation. In this case theshort-circuit protection is provided by the back-up fuses.

The non-directional earth-fault unit protectsboth the motor and the feeder against earth-faults. In solidly or low resistance earthed net-works, the neutral current can be derived fromthe line CTs when these are wired into a residualconnection and the operating time for the earth-fault protection is then normally set to a lowvalue, e.g. 50 ms.

In a contactor controlled application, the earth-fault unit is blocked when the line currents ex-ceed a preset value of four, six or eight times thefull load current setting of the thermal unit. Thisis done in order to avoid destruction of the con-tactor, which cannot break these high currents.The trip is in this case handled by the backupfuses. This blocking feature can also be used toensure that the unit will not cause nuisancetrippings even though the line CTs should par-tially saturate during a start-up, causing a vir-tual neutral current. The sensitivity of the earth-fault unit is typically set at 15...40% of the ratedcurrent of the motor.

4

Some notes anduseful hints

Connection withtwo phase currenttransformers

If phase current transformers are used only intwo phases, a third current is recommended tobe summed from the currents of these phases.This current is conducted to the input circuitof the missing phase. This procedure has two

advantages, i.e. the phase failure protection doesnot have to be disconnected and the measure-ment of the load currents is more accurate thanin a two-phase measurement.

Stabilizing for virtualearth-fault currents

The apparent neutral current caused by the dif-ference of the phase current transformers con-nected in parallel may cause an unnecessary op-eration of the earth-fault unit, especially in anoverload situation. This can be avoided by us-ing a stabilizing resistor R in the neutral cur-rent circuit. The resistor must have a continu-

ous power rating of e.g. 30 W and can have aresistance value of e.g. 100 Ω for the 1 A inputversus 10 Ω when the 5 A secondary input isused. The value of the knee-point voltage mustbe checked > 2 x Ustab. The stabilizing resistorwill also slightly reduce the E/F sesitivity.

Problems with falseE/F or U/B tripsduring start-up

If the unbalance or earth-fault units cause falsetrippings during a start-up e.g. because of mainCT saturation or severe amounts of harmonics,the units can be blocked by a control from thestarter over the external control input. If no

control signal is available, in some cases the startinformation available from the realy itself canbe used for this blocking purpose by feedbackto the external control input.

A core balance transformer is recommended tobe used in networks with isolated neutral or inhigh resistance earthed networks. The trans-forming ratio of the core balance transformercan be freely selected according to the earth-fault current and, consequently, the sensitivityof the earth-fault protection too. Due to the ex-tremely small burden of the relay, very smalltransforming ratios may be used in the cablecurrent transformers, in a KOLMA type trans-former even as small as 10/1 A. A transformingratio of at least 50/1 A or 100/1 A is recom-mended to be used. The setting of the earth-fault unit is typically selected in the range5...30% of the fully developed earth-fault cur-rent and a typical trip time could be 0.5...2 sec.The phase unbalance unit monitors the currentasymmetry of the network and protects themotor against heavy network unbalance or sin-gle-phasing. The phase unbalance unit is stabi-lized against maloperation due to heavy currentsand also allows a higher degree of unbalancewhen the motor is running at a load less thanthe full load current. The operating time of theunit follows an inverse time characteristic.

A separate unit checks for phase reversal condi-tions and operates within a fixed time of 600ms on a wrong phase sequence.

The unbalance and phase reversal units can beseparately selected or taken out of use. If e.g. amotor is used also with a reversed direction ofrotation, the phase reversal is taken out of serv-ice and does in this way not cause a trip whenthe direction is reversed.

The undercurrent unit operates upon a suddenloss of load. The unit is used e.g. for submers-ible pumps, where the cooling is based on a con-stant flow of liquid. If this flow is interrupted,the cooling capacity of the motor is reduced.This condition is detected by the undercurrentunit, which trips the motor.

The start-up totalling counter constitutes an-other way to control the number of start-upattempts within a certain time and can be set tocomply with the motor manufacturers´ state-ments on start-up number limiting.

By using the memorized fault parameters a com-prehensive after-fault analysis can be performedand a continuous follow-up of the start-up andother parameters can give good indicationsabout the condition of the motor.

The serial communication facilities finally makeit possible to achieve all the measured andmemorized parameters in the easiest possibleway, direct to a control room or a similar place.

5

Increasing thesensitivity of theearth-fault protection

The sensitivity of the operation of the earth-faultprotection can be increased by using the 1 A in-put instead of the 5 A input. This is possible in a

solidly earthed network too, because the thermalwithstand is normally high enough when using atripping earth-fault protection.

Optimizing theneeded time leftto restart

The approximate time until a restart is allowedcan be read out from register 9 on the measur-ing module. Also note that this value is updatedeven when the motor is in service. For a motorwith a long cooling time this can give valuableinformation on how to cool down the motorbefore shutdown in order to reduce the needed

downtime before restart. If possible, the motoris allowed to run with a minimum load thusthat the register showing necessary time to re-start has been reduced to a suitable value. Anidling time of e.g. 15 minutes can save an hourin cooling at standstill.

Time constant versussafe stall time t6x

If the thermal unit is to be set according to thesingle time constant of an object the time con-

stant can be calculated as: τ = 32 x t6x. This iscorrect provided that the factor p is set at 100%.

External trip viacontrol input

If an added function is needed, e.g. under-voltage, RTD-trip or a similar, an external re-lay can be linked to trip via the control input(SGB/5 = 1). The benefits are that the exter-nal relay can have a light duty output relay be-cause the trip is carried out by the SPAM.

Furthermore all event and memorized infor-mation from the trip instant can be achievedfrom the SPAM 150 C also over the commu-nication link.

Disabling of restartinhibit for use outsideSPAM 150 C

A switch SG4/2 can be used to lock out the re-start enable signal when the module SPCJ 4D34is used in other packages than SPAM 150 C. Thismight often be necessary as the restart enable sig-

nal can otherwise interfere with a trip output.The switch is found in submenu position 4 inthe register "A" and is normally = 0 but shouldbet set = 1 to disable the restart inhibit signal.

Mutual restartinhibit for multi-motor applications

If a number of large motors are run in a weaknetwork, a simultaneous start of two or moremotors may cause complete network break-down. Under these circumstances a restart in-hibit logic is needed and the easiest way to ob-tain such an arrangement is to link the start-up

information from each motor relay to the ex-ternal control input of all the other relays andto program the inputs to operate as restart in-hibit inputs. In this way the start-up of onemotor always prevents a simultaneous start ofany one of the other motors.

Note about thecontactor versuscircuit-breaker drives

Different output relay cards needed for contac-tor versus circuit breaker controlled drives:

Power and output relay modules type SPTU 240R2 and SPTU 48 R2 comprise normally opentrip contacts for circuit breaker operation where-as modules SPTU 240 R3 and SPTU 48 R3have a normally closed trip contact for contac-tor controlled drive use. When ordering the re-lay, this power module type as well as the relayrated frequency are indicated by the RS-numberof the relay.

The actual RS-numbers for SPAM 150 C are:

For circuit-breaker drive applications:RS 641 014 - AA ;50 Hz, 80...265 V ac/dcRS 641 014 - CA ;50 Hz, 18...80 V dcRS 641 014 - DA ;60 Hz, 80...265 V ac/dcRS 641 014 - FA ;60 Hz, 18...80 Vdc

For contactor drive applications:RS 641 015 - AB ;50 Hz, 80...265 V ac/dcRS 641 015 - CB ;50 Hz, 18...80 V dcRS 641 015 - DB ;60 Hz, 80...265 V ac/dcRS 641 015 - FA ;60 Hz, 18...80 Vdc

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Example 1.Protecting acircuit breakercontrolled motorin an isolatednetwork

Given data of the squirrel cage motor to be pro-tected:

Rated power Pnm 4500 kWRated voltage Unm 3300 VRated current Inm 930 A

Starting current Is 6.2 x InmStarting time ts 11 sStall time permittedunder cold conditions 19 s

Ambient temperature 20°C

C.T. current ratio 1000 /1ANetwork earth-fault current atfully developed fault (100 % e/f ) 10 AEarth-fault sensitivity required 20 %

Calculation of settings:Due to the ambient temperature <40°C, the fullload current (FLC) is increased by 5%:

FLC = 1 .05 x 930 A

The relay setting Iθ is then

Iθ / In = = 0.98

The motor is directly started, .i.e. p = 50 %.

The setting t6x is selected from the time/cur-rent characteristic corresponding to a hot mo-tor condition. This will enable one hot / twocold starts.

First the ratio between the starting current andthe full load current is calculated :

Is / Iθ = Is / ( 1.05 x Inm) = 6.2 / 1.05 ≈ 5.9

A setting t6x ≈ 25 s is selected, permitting a start-ing time which is a few seconds longer than thegiven motor starting time.

As the safe stall time is longer than the start-uptime no speed switch arrangements are needed.For a single startup from a cold condition, thethermal unit would trip only after about 25 sec-onds, which is longer than the permitted 19 sec-onds. A single startup is instead protected bythe startup supervision, i.e. Is

2 x ts. The start-ing current is set directly to the value Is= 6.2 x930 A x 1/1000 ≈ 6.1 x In, whereas the startuptime is set at about 10% above the normalstartup time in order to give a safety margin forthe operation. Thus ts is set at 11 s x 1.1 ≈ 12 s.

The prior alarm setting can be selected e.g.Θa=80...90 % for a reasonably early alarm.

Fig. 1. How to find the setting t6x from the hotthermal curve

As the start-up consumes 11 s / 25 s ≈ 45% ofthe full thermal capacity, the restart inhibit levelΘi must be set lower than 55%, e.g. at 50%.

The cooling factor kc is set e.g. at 4 because themotor is a normal, totally enclosed unit, cooledby a fan on the the rotor shaft.

If we want the high-set overcurrent to doubleas a running stall protection, the basic settingshould be lower than the startup/stall currentand be doubled during start. Thus this elementcan be set to a value of 75 ...90 % of Is:

I>> = 0.75 x 6.2 x 930 A x 1 / 1000 ≈ 4.3 x 1A.Doubling during the start-up -> SGF/2 =1.

Generally a setting as low as 75% should be giv-ing good results but if the inrush current shouldcause trippings during startup, a higher settingmust be chosen.

For the earth-fault a core balance transformerwith a CT ratio of 100 / 1 A is used.

The earth-fault protection should detect anearth-fault of 20% of the fully developed faultcurrent, i.e.: 20% x 10 A = 2.0 A

I0 = 2 A x 1 A / 100 A = 2.0% x 1 A

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The possibility to use an external trip is alsoindicated in the block diagram in Fig. 2. By set-ting switch SGB/5 = 1, the control input islinked to the trip output. In this case e.g. anundervoltage relay can be used to supervise thebusbar voltage and will in a fault condition per-form a trip using the SPAM 150 as an inter-face. In this way all signals, events and memo-rized parameters can be accessed via this relay.

The earth-fault unit is energized from a corebalance CT in order to obtain a sensitive earth-fault protection. Because of the low input im-pedance of the relay a low turns ratio of the corebalance c. t. can be used . When using the core

balance c.t. type KOLMA 06 A1, a turns ratioof 100 /1 A is recommended.

The high-set overcurrent unit constitutes aninterwinding short-circuit protection for themotor and a phase-to-phase short-circuit pro-tection for the feeder cable. The current settingis automatically doubled during start-up. Thusthe current setting can be given a value lowerthan the motor starting current. Normally thesetting can be chosen to 0.75 times the motorstarting current. With a suitable operating timeset, this feature will enable the high-set over-current unit to operate, if the motor is jammedwhile the motor is running.

Figure 2. A circuit-breaker controlled drive in an isolated net with core balance approach for theearth-fault protection.

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The behaviour of the thermal model under acouple of typical drive conditions is shown inFig. 3 and 4. Figure 3 shows the thermal behav-iour during a dual start-up sequence from a fullycold state. During the first start-up, the startcurrent is heating up the motor during the starttime and a total of about 65% of the thermalcapacity is used. After the start, the motor isleft running for a few minutes with a normalload of about 90% of the full load current. Assoon as the motor leaves the start-up condition,the hot spots start levelling out and the used

thermal capacity decreases rapidly to a level de-termined by the long term thermal loading ofthe motor. The second start brings the thermalcapacity used up to a level close to tripping butstill allows the motor to run up. After the sec-ond start the motor is left running for a longtime with a normal load and we can see the ther-mal capacity curve level out, first by eliminat-ing the hot spots and then by successive cool-ing to a steady state where about 37% of thethermal capacity is used.

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First start-up11 s at 6.2 x Iθ

Second start-up11 s at 6.2 x Iθ

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Running continuouslyat 0.9 x Iθ

Fig. 3. The thermal behaviour for two cold starts followed by a motor running at normal load.

Figure 4 shows a situation where the motor hasbeen running for a long period, whereafter it isoverloaded until the relay carries out a trip. Therestart enable relay is reset as the thermal levelis higher than the set level, which in this case is40%. The motor begins to cool down, first bylevelling out hot spots and then by slowly re-ducing the thermal curve now mainly consist-ing of used thermal capacity due to a long termthermal overload. As the motor is at standstill,

the cooling rate is reduced as the cooling fan onthe motor shaft is not running. The reducedcooling is also taken into account by the relayby a suitable setting of the cooling time multi-plier kc, e.g. 4 ....8. When the used thermal ca-pacity has fallen below the set restart inhibit level40%, the restart enable relay of the motor pro-tection is activated and the motor can again bestarted.

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Overload leading to a thermal trip.Time in minutes

Cooling at standstill.Time scale in minutes.

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Motor running. Time in minutes.

Fig. 4. The thermal behaviour of an overload trip and cooling, followed by a motor restart.

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Example 2

Determiningsuitable settingvalues for astandard,contactorcontrolled directstarted motor

Data on the motor to be protected:

Type = squirrel cage motor with direct start,totally enclosed with fan cooling

Rated power Pnm 900 kWRated voltage Unm 380 VRated current Inm 1650 AMotor directly started, i.e. p = 50%Starting current Is 6.0 x InmStarting time ts 9 sTwo starts from cold requiredMax. stall time from cold condi. 21 sAmbient temperature 20°CC.T. current ratio 2000/1A

Network solidly earthedEarth-fault sensitivity required 20% of Inm

Calculation of settings:Due to the ambient temperature <40°C, the fullload current (FLC) is increased by 5%:

Thus FLC = 1 .05 x 1650 A = 1733 A

The relay setting Iθ is then:

Iθ / In = = 0.87

The motor is direclty started, i.e. p = 50%.

The setting t6x is selected from the time/currentcharacteristic corresponding to a hot motor con-dition. First the ratio between the starting cur-rent and the full load current is calculated :

Is /Iθ = ( 6.0 x 1650 A)/(0.87 x 2000 A) = 5.7

The starting current 6.0 x 1650 x 1/2000 ≈5.0 isused together with the starting time 9 s + 10 …15%safety margin = 10 s to set up the startup supervi-sion, based on Is2 x ts .

As the start-up time is smaller than the maxi-mum motor safe stall time of 21 seconds, nospeed switch inhibited stall protection is needed.

A setting t6x = 15 s is selected from the hotcurve (see Fig. 5), permitting a starting timewhich is a bit longer than the given motor start-ing time. The corresponding time read out fromthe cold curve gives a trip time of about 16seconds.

The prior alarm setting can be selected e.g.Θa = 85 ...90 % for a reasonably early alarm.

As the start-up consumes 9s/15s ≈ 60% of thefull thermal capacity, the restart inhibit level Θimust be set at 40% or lower.

The cooling factor kc is set at 4...6 beacuse themotor is a normal, totally enclosed unit, cooledby a fan on the the rotor shaft.

As the drive is contactor-controlled and the con-tactor cannot break a high current fault, thehigh-set overcurrent unit must be set out of op-eration.

The earth-fault setting is calculated as:I0/In = 0.2 x 1650 A / 2000 A = 16%.

1.05 x 1650 A x 1 A 2000 A x 1 A

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The trip time for an earth-fault is set at 50 msas the network is solidly earthed.

Because the drive is contactor controlled, theearth-fault unit must be blocked at high cur-rents. Whenever the phase currents exceed e.g.6 times the setting Iθ, the earth-fault unit isblocked in order not to operate the contactorat too high current levels. During the high cur-rent conditions the protection is based on thebackup fuses. The limit for the blocking cur-rent is set by means of the switches SGF/3 andSGF/4.

The thermal unit with a set value of p = 50% isnormally used to describe the thermal capacityof a directly started motor.

The feeding network is solidly earthed and thusthe operation of the earth-fault protection is se-lected to be tripping.

10

Should a unit other than the overload protec-tion or start-up stress monitor of the relay trip,the condition of the motor should be checked.For that reason the operation of the output re-lay A (contacts 65 - 66) is selected to be manu-ally reset after a trip by means of switch SGB/7.If the latching function is wanted for all tripoperations, switch SGB/8 is used instead of theformer switch.

Simultaneously with the trip relay, a signallingrelay B is operated, giving a trip signal over con-tacts 68 - 69.

A prior alarm for a beginning overheating is

achieved with relay D (contacts 77 - 78) as soonas the thermal level exceeds the set prior alarmlevel θa. This level can preferably be set at e.g.90%, allowing the motor to be fully utilized atnominal current, but giving an alarm as soon asthe load is constantly higher than the full loadcurrent.

A too rapid restart attempt is prevented by therestart inhibit feature in the relay.The close sig-nal to the contactor or circuit breaker is linkedover the restart enable relay E contact (74 - 75).The relay will not allow a restart until the ther-mal level of the motor is lower than the set re-start inhibit level θi.

Figure 6. A contactor controlled motor drive with residually connected earth-fault protection. Tostabilize against virtual earth-faults an external resistor is added in the return path for the earth-fault current to increase the burden for the main CTs.Note! A power and output relay module type SPGU 240 R3 or SPGU 48 R3 is used for a nor-mally closed trip contact for contactor controlled drive use.

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67

89

1 A

5 A

7071

72R

x T

x65

66

IRF

6869

7778

7475

8081

1011

11

SG

B/1

SG

B/2

SG

B/7

SG

B/8

SG

B/3

TR

IPR S

EA

L-IN

Σ > ts

1

+

B

+

C

+

F

+

E

+

D

+

A

3

SG

B/4

STA

LL

I/O

I» Io> I<

STA

RT

∆I

I t2

RE

STA

RT

INH

IBIT

R

ES

TAR

TIN

HIB

IT

SG

B/5

RE

LAY

RE

SE

T

θ>θ i

θ>θ a

θ>θ t

SG

B/6

EX

TE

RN

AL

TR

IP

U1

S

PC

J 4D

34

U3

SP

TK

4E

3

U2

S

PT

U _

R2

ss

BL

OC

K D

IAG

RA

M W

ITH

FA

CT

OR

Y

SE

TT

ING

S O

F S

WIT

CH

ES

SG

R

SPA

M 1

50 C

I

0

–

+

Example 3

Protecting adirect startedmotor with a lowsafe stall time

In many applications, e.g. ExE-type drives, themotor is not allowed to be in a stalled condi-tion as long as its own start-up time. To findout whether the motor is speeding up or not, aspeed switch on the motor shaft is used. Theswitch should be open at standstill and closewhen the motor speeds up.

The speed switch information is used to controlthe start-up stress monitor and the setting ts isset a little shorter than the maximum allowedjam time te. If the motor starts accelerating, thespeed switch will inhibit the start-up supervisionunit trip and leave the protection to the thermalunit. If the motor does not speed up, trippingwill be carried out after the time ts = te.

The speed switch should be open at standstill and close when the motor speeds up.

Fig. 7. Protection of a directly started motor. A speed switch on the motor is used to produce asecure stall protection even though the maximum safe stall time of the motor is less than the start-up time.Note that because of the fact that only two phase CTs are used, the third phase is reconstructed bysumming the two monitored currents through the third winding.

12

Example 4

Protecting of afeeder cable, atransformer oranother non-rotating object

The relay SPAM 150 C can also be used as amultifunction protection for other objects thanmotors, e.g. feeder cables, resistive elements ortransformers. For this purpose some featureshave lately been added to the original versionof the relay.

As the start-up supervision stage in these appli-cations more or less always is used as an over-current unit with definite time or I.D.M.T op-eration, there was a need to have a shorter set-ting than 2.0 s. For this reason the setting rangefor the operating time was extended to a range0.3....80 seconds.

If an I.D.M.T. operation is wanted, the start-up thermal stress unit can be used to performan operation similar to the extremely inverse.Normally the operation of this unit is tied to amotor start-up condition. For other applicationsthis is not very useful and for this reason thestarting condition for the unit was madeselectable with a switch SG4/1, found in thesubmenu, step 4 of register "A" on the relaymodule SPCJ 4D34.

With the switch SG4/1 in position "1", the start-ing criterion for the thermal stress unit isswitched from the normal, where the currentmust change from 0.12 x Iθ to 1.5 x Iθ withinless than 60 ms for the unit to start, to a condi-tion of activating the unit any time as soon asthe setting Is is exceeded. With switch SG4/1in the default position (="0"), the unit workswith a normal motor start-up operation relatedabove.

If the measuring module SPCJ 4D34 is usedin another protective combination than SPAM150 C, the restart enable signal might inter-fere with trip signals from neigbour modulesconnecting to the same pins on the motherboard. To avoid this, a means of inhibiting therestart enable signal has been implemented.When switch SG4/2 is set from its default po-sition "0" to position "1", the restart enablesingal output is cut off and hence no signal islinked to the mother board.

A start signal from the low-set overcurrent unitto the start output relay is in certain applica-tions needed to form the blocking signal for abusbar protection of type blocked O/C relays.This signal can now be linked to output relayD (SS1) by setting switch SG4/3 to position"1".

The high-set overcurrent unit constitutes theshort-circuit protection and can be used withsettings down to 0.5 x In and with trip timesdown to 40 ms.

The start of the high-set overcurrent unit canbe brought out linked to relay D instead of themotor start-up info. This is done by settingswitch SGR/3 =1 and SGR/1=0. Now the startsignal can be used as a blocking signal for anupstream feeder protection relay, thus consti-tuting a busbar protection based on blockedovercurrent relays.

The use of a core balance transformer for meas-uring the earth-fault current makes the earth-fault protection very sensitive. When using acore balance transformer the variations in theload current do not interfere with the measur-ing. Thus a relatively small earth-fault currentcan be selected for a resistance earthed network.

If a residual connection is preferred, this canalso be used even though the settings then mustbe a bit higher in order to avoid possible stabil-ity problems due to unbalances in the maintransformers causing virtual earth-fault currentsduring high phase current conditions. Also notethe possibility to use an external stabilizing re-sistor for helping up too weak main transform-ers, preventing them from causing these falseearth-fault currents.

The thermal unit with a weighting factor set-ting of p = 100% is suitable for describing thethermal capacity properties of devices with nohot spot behaviour, i.e. for cables or similar ob-jects.

The thermal unit is used in a normal way forprotecting against long time overloading andoperates in a single time constant mode. Thesetting of p = 100% means that the heating andcooling of the protected object is always similarregardless of the current levels. When settingthe time constant for the relay the expressiont= 32 x t6x can be used. A thermal prior alarmcan be achieved over a separate output relay, e.g.relay C.

The behaviour of a thermal model with p =100% is shown in Fig. 8. The load is intermit-tent with high load sequencies with currents of1.5 x Iθ and low load sequencies with a currentof 0.8 x Iθ. As can be seen, the heating and cool-ing parts of the curve are behaving in a similarway with the same time constant. Normally thecooling constant kc for very low currents, cor-responding to a motor standstill is set at 1.

A typical connection for a cable protection ap-plication is shown in Fig. 10.

13

0

20

40

100

60

80

%

1.5 x Iθ 1.5 x IθI = 0.8 x Iθ I = 0.8 x Iθ 1.5 x Iθ I = 0.8 x Iθ

Figure 8. The behaviour of the thermal level in a single time constant object with varying loadsequencies

The parameter p ofthe thermal unit

One of the main settings of the thermal unit isthe thermal unit weighting factor p. This para-meter is picturing the dualism of the thermalproperties of a motor.

A setting of p=100% produces a pure single timeconstant thermal unit, which is useful for ap-plications with cables etc. As can be seen fromFig. 9., the hot curve with p=100% only allowsa stall time of about 10% of the cold safe stalltime. For a motor with a curve of e.g. t6x = 10 s,the hot trip time would be only 1 s, whereas themotor can withstand at least 5 or 6 seconds. Toallow full use of the motor a lower p-valueshould be used.

As about one half of the thermal capacity isnarmally used when a motor is running at nomi-nal load, this must also be handled by the pro-tective unit. With the normal motor setting ofp=50 %, the relay will notify a 45...50% ther-mal capacity usage at full load.

Generally a choice should be made between50% for a standard motor started directly online, and 100% for a non-rotating object or asoft-started motor. Only in special cases, wherea closer adjustment of the thermal characteris-tic is needed and the thermal capacity of theobject is very well known, a value between 50and 100% might be needed.

Note! For applications with e.g. three cold vs. twohot starts a setting of p = 40% has sometimesproved to be useful. Otherwise setting the p-valuemuch below 50% should be handled carefully be-cause in this case there is a possibility to overloadthe protected object as the thermal unit might al-low too many hot starts or "forget" too much of thethermal history background. In Fig.9. you can seethat the hot curve of p = 20% is quite close to thecold curve. The cold curve is identical for all p-values.

Figure 9. The influence of the p-value on thehot trip time curve with t6x = 20 seconds.

100

500

200

50

10

20

5

1

2

3

4

30

40

300

400

1 2 3 4 5 106 8 I/Iθ

1.05

p [%]

20

50

75

100

Cold curve

14

L1

L2 L3

Uau

x

Inte

rnal

Rel

ayF

ault

+ -

0-

I-

I0

+

Rec

onn.

Ena

ble

The

rmal

Prio

rA

larm

Trip

Sig

nal

Trip

Out

put

Rel

ay

Ext

erna

lC

ontr

ol In

put

6362

61

1 A

5 A

1 A

5 A

1 A

5 A

2526

271

23

45

67

89

1 A

5 A

7071

72R

x T

x65

66

IRF

6869

7778

7475

8081

1011

11

SG

B/1

SG

B/2

U1/

SG

B/7

U1/

SG

B/8

SG

B/3

TRIP

R SE

AL-

IN

Σ > ts

1

+

B

+

C

+

F

+

E

+

D

+

A

3

SG

B/4

STA

LL

I/O

I» Io> I<

ST

AR

T

∆I

I t2

RE

ST

AR

TIN

HIB

IT

RE

ST

AR

TIN

HIB

IT

SG

B/5

RE

LAY

RE

SE

Tθ>θ i

θ>θ a

θ>θ t

SG

B/6

EX

TE

RN

AL

TR

IP

U1

S

PC

J 4D

34

U3

SP

TK

4E

3

U2

S

PT

U _

R2

ss

BL

OC

K D

IAG

RA

M W

ITH

FA

CT

OR

Y

SE

TT

ING

S O

F S

WIT

CH

ES

SG

R

SP

AM

150

C

Not

e!S

GB

/ 5 =

1

Figure 10. Protection of a feeder.

15

Example 5

How to use thestart-up timecounter

Quite often a motor manufacturer gives a state-ment of how many times a motor may be re-started within a certain time interval. The start-up time totalling check acts as a backup to thethermal protection by keeping track of that re-starts cannot be made too frequently, in otherwords that the recommendations from themanufacturer are not exceeded.

The start-up time counting possibility is inte-grated in the module SPCJ 4D34 so that noextra timers are needed. To use the start-up timecounter, two settings must be worked out. Firstwe must define the restart inhibit level in startseconds and further we must tell the modulehow rapidly the accumulated amount of startseconds should be counted down.

Let us for example assume that our motor isrecommended to be started at the most for threetimes within 8 hours and that the start-up timeis 20 seconds each. By making all the allowedthree starts in a row we will get the situationdescribed in the diagram below.

The three 20 second starts add up to a total of60 seconds. Right after the third start has beeninitiated, the inhibit should be activated as afourth start attempt is no more allowed. Thismeans that the setting of the inhibit level in thiscase is set at 41 seconds. Please note that thestart sequence will still proceed even though theinhibit is activated. The inhibit is only inter-rupting the close path to the circuit-breaker, thuspreventing further start-ups.

Furthermore the statement of not more thanthree starts within 8 hours means that the count-down should reach the inhibit level after 8 hoursto allow for a single new start. In our examplethis means that we should count down 20 sec-onds in 8 hours, i.e. the countdown rate settingis ∆∑ts/∆t = 20 s / 8 h = 2.5 s / h.

Please note that for readability reasons, the timescaling in the diagram is not the same for thestart-up versus cooling-down sequences!

∑ts

[s]

t0

10

20

30

40

50

Next start possible

Start 1

Start 2

Start 3

Restart inhibit activated above 41 s level

8 h

Figure 11. The operation of the start-up time counter.

16

Example 6

How to set thephase unbalanceand phasereversal unit

The phase unbalance and phase reversal unit inSPAM 150 C is based on the measurement ofthe difference between the three phase currents.The difference between the highest and the low-est phase current is compared in per cent of thehighest one.

The benefits with this arrangement is a lowersensitivity to frequency variations and harmon-ics in the currents. Furthermore the phase re-versal protection is separated as a stand-aloneunit not dependent of the asymmetry protec-tion.

In a full broken phase condition, the unbalancereading of SPAM 150 C is 100%. This can becompared to the reading of 57.8% with a relaymeasuring unbalance on a negative phase se-quence current basis (e.g. SPAM 110). Thuswhen comparing n.p.s. values to current differ-ence values, a conversion factor of 0.578 is used.

Example:

We want to have an unbalance unit sensitivityof about 15% in terms of negative phase se-quence current on a motor. The unbalance pro-tection should operate with an operating timeof 10 s at the 15 % amount of unbalance.

We calculate:15% (NPS) = 15 / 0.578 ≈26 % (∆I )

Thus we can set ∆I> =25% on the relay

From the trip time chart we can see that a triptime of the desired 10 s at 25% is achieved byusing a time setting t∆ of 60 s. The unbalanceunit will not operate for unbalance levels belowthe set 25% but at this level the trip time is10 s and for higher degrees of unbalance thetime decreases down to 1 s at a full single phas-ing condition.

The phase unbalance unit is selected to be op-erative with the switch SGF/5 =1 and the phasereversal protection is made operative with switchSGF/6 = 1.

Finally the output relay is selected with switchesSGR1/5 or SGR2/5.

∆I/ IL [%]

100

80

60

50

40

30

20

10

8

6

5

4

3

2

1

ts

120

20

40

80

60

100

120

t∆ s

10 20 30 40 50 60 70 80 90 100

Figure. 12 The trip time diagram for the phaseunbalance unit.

17

SP

AM

150 C

6370

7172

6566

6869

7778

7475

8081

1011

11

SG

B/1

SG

B/2

SG

B/7

SG

B/8

SG

B/3

TR

IPRLA

TC

HIN

G

1

+B

+C

+F

+E

+D

+A

SG

B/4

11

SGR1/8

SG

B/5

SG

B/6

U1 S

PC

J 4D34

U3 S

PT

E 4E

3

U2 S

PT

U _ R

2

IRF

Σ >ts

3

STA

LL

I/O

I>>

Io>I< ST

AR

T

∆I R

ES

TAR

TIN

HIB

IT

RE

STA

RT

INH

IBIT

RE

LAY

RE

SE

T

θ>θi

θ>θaθ>θ

t

EX

TE

RN

AL T

RIP

I x t2s

s

2526

271

23

45

67

89

1 A5 A

1 A5 A

1 A5 A

1 A5 A

6162+

-

~

SGR1/7SGR1/6SGR1/5SGR1/4SGR1/3SGR1/2SGR1/1

SGR2/8SGR2/7SGR2/6SGR2/5SGR2/4

SGR2/3SGR2/2SGR2/1

SG4/3

I >s

SG4/2 TS

1S

S1

SS

2S

S3

TS

2

Appendix 1

The complete blockdiagram for SPAM150 C with all SGRswitches shown

18

Appendix 2

Trip characteristicdiagrams for thethermal unit

cold

.fh4

t/s

1000

100

500

200

50

10

20

5

1

2

3

4

30

40

300

400

2000

3000

4000

t6x [s]

120

60

30

20

15

10

5

2.5

1.05

1 2 3 4 5 106 8 I/Iθ

100

200

50

10

20

5

1

2

3

4

30

40

1 2 3 4 5 106 8 I/Iθ

1.05

t6x [s]

120

60

30

20

15

10

5

2.5

t/s

1000

500

300

400

2000

3000

4000

20ho

t.fh4

Trip diagram for a cold condition, i.e. with-out prior load. The cold curve is independ-ent of the setting of the p-value

Trip diagram for a hot condition, i.e. with aprior load 1.0 x Iθ and weighting factor p setat 20%

19

t/s

1000

100

500

200

50

10

20

5

1

2

3

4

30

40

300

400

2000

3000

4000

2 3 4 5 106 8 I/Iθ

1.05

t6x [s]

60

30

20

15

10

52.5

120

1

50ho

t.fh4

Trip diagram for a hot condition, i.e. with aprior load 1.0 x Iθ and weighting factor p setat 50%

t/s

1000

100

500

200

50

10

20

5

1

2

3

4

30

40

300

400

2000

3000

4000

1 2 3 4 5 106 8 I/Iθ

t6x [s]

120

60

302.5 5 10 15 201.05

100h

ot.fh

4

Trip diagram for a hot condition, i.e. with aprior load 1.0 x Iθ and weighting factor p setat 100 %

20

Solving the equation for heating up with refer-ence to trip time gives:

t ≈ 32.15 x t6x x ln

In the above expression It is the trip current level,which is always 1.05 x Iθ , i.e.:

t ≈ 32.15 x t6x x ln

Appendix 3

Mathematicalequations forthe thermal unit

Heating up during an overload condition:

ΘA = (I / (1.05 x Iθ))2 x (1-e -t/τ) x 100%

ΘB = (I / (1.05 x Iθ ))2 x (1-e -t/τ) x p%

Cooling at normal load or in a standstill condi-tion:

When the current decreases below 1.0 x Iθ, thethermal curve A is linearly brought down tothe level of the thermal history curve B as shownin curve part C. This corresponds to the level-ling out of the hot spots in the motor.

Thereafter the cooling follows the lower curvewith a time constant equal to the heating timeconstant as long as the motor is running at nor-mal load or idling.

For a motor at standstill, i.e. when the current isbelow 12% of Iθ, the cooling can be expressedas:

Θ = Θ02 x e -t/kc x τ

where Θ02 is the initial thermal level and kc isthe cooling time multiplier according to the setvalue 1...64.

0

20

40

100

60

80

%

A

B

C

D

Θ02

Estimated trip time(modified 2003-04)

The parameters Iθ , t6x and p are the relay set-tings, Ip is the long term prior load and finally Iis the overload current which is finally going tocause a trip. The operand ln is the natural loga-rithm (log e ).

The thermal level is handled twice a second inthe relay, giving a best trip time resolution of0.5 s.

(I/Iθ)2 - p /100 x (Ip/Iθ)2

(I/Iθ)2 - It /Iθ)2

(I/Iθ)2 - p /100 x (Ip/Iθ)2

(I /Iθ)2 - 1.1025

21

Appendix 4

Reference card forthe motor protectionrelay module SPCJ4D34

REFERENCE

CARD

Settings:

Asetteluarvot:Inställda värden:

Iθ = In

Is

= In

∆I = %IL

t6x

= s ts

= s t∆ = s

p = % I>>

= In

I<

= In

Θa

= % t>>

= s t<

= s

Θi = % I

o = %I

n∑t

si = s

kc

= to

= s ∆∑tsi

= s/h

Protected object: Relay type designation:Suojauskohde: Skyddsobjekt: Releen lajim.: Reläets typbet.:

Code of apparatus: RS-number:Kojetunnus: Apparatkod: RS-numero RS-nummer:

Date & signature: Serial number:Pvm. & allek.: Datum & sign.:_________________________ Sarjanumero: Serienummer:

1 x 1 =2 x 2 =3 x 4 =4 x 8 =5 x 16 =6 x 32 =7 x 64 =8 x 128 =

∑∑∑∑ =

1 x 1 =2 x 2 =3 x 4 =4 x 8 =5 x 16 =6 x 32 =7 x 64 =8 x 128 =

∑∑∑∑ =

SGF1 x 1 =2 x 2 =3 x 4 =4 x 8 =5 x 16 =6 x 32 =7 x 64 =8 x 128 =

∑∑∑∑ =

SGB1 x 1 =2 x 2 =3 x 4 =4 x 8 =5 x 16 =6 x 32 =7 x 64 =8 x 128 =

∑∑∑∑ =

SGR1 SGR2

Instr. transf.ratios:Mittamuunt. muuntosuhteet:Mättransf. omsättning:

IL / A

Io / A

Remarks:Huom.: Anm.:

1 >

2 >

3 +∑tsi +4 I>>

5 ∆I

6 I x t7 Io

8 I<

9

0OPERATION IND.

2

θθθθ θθθθθθθθθθθθ

θθθθ

EXT. TRIP

EINHi

a

t

A reference card similar to the one shown above is delivered with each relay. The reference card isthe best place to store all information about the relay settings etc. Please fill in the card thorouglyand keep it together with the protective relay for quick reference.

SYKW 974

SPCJ

4D34 Switchgroup SG4Password

Ists

4

Latest memorized, event (n)value of phase current IL11 1 2

Latest memorized, event (n)value of phase current IL22 1 2

Latest memorized, event (n)value of phase current IL33 1 2

5 1 2

6 1 2

7 1 2

9 1

8

Status of external relay blocking / control signal0

Communication speed [kBd]

Bus supervisionRelay module address A 1 2

0 000 θ I>> Io>

MAI

N

MENU

REV

STEP

.5s

FWD

STEP

1s

Latest memorized, event (n) value of neutral current Io

Previous event (n-1) value of current Io1 2

Latest memorized, event (n) value of unbalance ∆I

Previous event (n-1) value of unbalance

Latest memorized, event (n) value of startup stress

Previous event (n-1) value of startup stress

Recent value of thestartup time count ∑t

Approximate time t beforea restart attempt is enabled

Latest memorized, event (n) final value of thermal level θ

Previous event (n-1) final thermal level

MAIN MENU SUBMENUS

STEP 0.5 s PROGRAM 1 sSUBMENUS

FWD. STEP 1 s REV. STEP 0.5 s

3

3

3

3

3

3

3

3

θt a I∆ I< ∑ts

Duration of latestactivation of unit I>

Duration of previousactivation of unit I>

Duration of latestactivation of unit I>>

Duration of previousactivation of unit I>>

Duration of latestactivation of unit I<

Duration of previousactivation of unit I<

Duration of latestactivation of unit Io

Duration of previousactivation of unit Io

Duration of latestactivation of unit ∆I

Duration of previousactivation of unit ∆I

Motor startupcount at event (n)

Motor startupcount at event (n-1)

Thermal level beforethe latest event (n)

Thermal level beforethe prior event (n-1)

Startup time t of thelatest motor startup

Counter for numberof service hours

32

Recent value θ of thethermal capacity used

1 Recent value of thephase unbalance ∆I

Previous event (n-1) value of phase L1

Previous event (n-1) value of phase L2

Previous event (n-1) value of phase L3

DATA REGISTERED DURING THE LATEST EVENT (n) DATA REGISTERED DURING THE PREVIOUS EVENT (n-1)

4

i

m

m

is

s

22

Appendix 5

Motor data enquiryform

Data needed to determine motor protection settings

System data

Ambient temperature tamb = °C

Cooling arrangements & systems:

totally enclosed (rib cooling)

heat exchanger

....................................................

Cooling time coefficient kc =

CT current ratio / A

Block transformer ratio / kVNote! If a block transformer is used, theratio of this transformer must also be noted!

Network earth-fault current

when fully developed (100%) A

Type of load.......................................

...............................................................

Motor data

Type or construction of motor............

.................................................................

Rated power Pnm = kW

Rated voltage Unm = V

Rated current I nm = A

Start-up arrangement:

direct on line transformer

reactance

Starting current I s = x Inm

Actual starting time t s = s

Max. start/stall time permitted

- from a cold condition = s

- from a hot condition = s

Required number of

cold / hot starts ___ ___

Special remarks & requirements.............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................The items marked with bold letters are completely essential to make itpossible to work out settings for the motor thermal and start-up protection.

23

1MR

S 7

5184

1-M

TI

EN

ABB OySubstation AutomationP.O.Box 699FIN-65101 VAASAFinlandTel. +358 (0)10 22 11Fax.+358 (0)10 22 41094www.abb.com/substationautomation