SEL-587 Training Notes

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Maintenance StandardProtection and Control

Title: Subject: SEL 587SEL 587 Relay

Supplementary Training Notes Number 42.87.731-8

1. Introduction

The SEL 587 relay provides two-winding transformer overcurrent and current differential'protection. The relay includes _

e a complete group of overcurrent elements for each winding. Each group is comprised ofphase and residual instantaneous elements as well as phase, negative sequence andresidual definite time and inverse time elements.

• restrained and unrestrained differential operate elements. The restrained operate elementhas two settable percentage restraint slope characteristics and can be blocked by second orfifth harmonic blocking elements. The unrestrained element can be used to quickly clear/ /high magnitude internal faults.

• ten SELogic Control Equations which provide two independent timers, tripping, eventreport triggering and relay output contact control.

2. OvercurrentProtection

Overcurrent elements associated with each winding are non-directional and measure onlyfundamental frequency. Elements can be externally torque controlled by setting INl or IN2 equal toeither TCEN (enable torque control) or TCBL (block torque control). The selected element is theneither torque-controlled enabled, or blocked, when the external input is asserted.

Phase overcurrent elements respond to the maximum phase current magnitude, lp, where Ip is thelargest value of [la], [Ib], and [lc].

Negative sequence elements respond to 312 current, where 312 = Ia + Ib(l/240) + Ic(lIl20).

The residual element responds to 310 current, where 310 = Ia + Ib + Ie.

3. "BifferentialProtection • I

3.1 DifferentialElementLogic

Figure 1 illustrates how the SEL 587 relay compares input winding currents IWDGI and IWDG2.First, input currents are scaled by the value of their associated TAP setting and then compensated,as required, for the given transformer / CT connection configuration (see 3.2 below). Resultantquantities are then added vectorially to give per unit operate current

lOP = IIWl/0 + IW2/<!>1.If0 = <!>+ 180°, then lOP = IIW.II-IIW21

and magnitudinally to give per unit restraint current

IRT = (lIWll + IIW21) / 2

\~----'---"---..--':"--------.----------r-----4--- .."...~,------'----iPrepared By PDS'~ I Recommended By DBB I Approved By GHYNK IIS'ocoDate 98Feb03 j ~§ 1 d 12

95,Jan20

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b Maintenance StandardProtection and Control

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Number 42.87.731-8

Subject SEL 587Title: SEL 587 Relay

Supplementary Training Notes

The METER DIF command, outlined in section 6 of the relay manual, displays the instantaneousmagnitudes of lOP and IRT in secondary amps, referred to Winding 1. Therefore, displayed valuesare lOP and IRT per unit quantities multiplied by TAPl setting.

IWDG1 r=L"l_---1Transformer/CT Connection f--_---(Amps) -~ Compensation +

~1 Transformer/CT Connection T

IWDG2 - TAP2 I----i Compensation 1--+----.----'(Amps)

lOP(MultiplesofTAP)

IW1 IW2

IW1 and IW2 quantities are in per unit of TAP

IIW11 + IIW21 IRT'- I-- (Multiples

'---- 2 ofTAP)

Figure 1 Differential Element Logic Diagram

3.2 Transformer and CT Connections (RelayCompensation)

The SEL 587 relay acknowledges fourteen (14) different combinations of power transformer andcurrent transformer (CT) winding connections as outlined in section 4 of the relay manual. Some ofthese combinations require phase adjustment between primary and secondary quantities; the relayprovides this compensation automatically.

Connecting a transformer in a delta-wye or wye-delta configuration shifts secondary voltages andcurrents 30° with respect to comparable, primary quantities. Conventionally, connecting associatedCTs in an opposite configuration compensates for this phase shift, i.e. CTs are connected delta-wyefor a wye-delta connected power transformer.

Prepared By P DS I Recommended By: DB B I Approved By GHYNK I Issue Date 98Feb03 I Pag>2 d 12

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b c Maintenance StandardProtection and Control

Number 42.87.731-8

Subject SEL 587Ti~e: SEL 587 Relay


With reference to Figure 2, note that the SEL 587 relay provides the option of using wye-wyeconnected CTs with wye-delta or delta-wye connected power transformers.

Assume that a power transformer is connected wye-delta and that the delta connection is an "A-C"style, i.e., A0 polarity is connected to C0 non-polarity; associated CTs are connected wye-wye.The relay obtains the connection configuration from the settings, TRCON = YDAC (Transformerconnection = wye, primary; delta, A-C secondary) and CTCON = YY (CT connection = wye-wye).Since the CTs are connected wye-wye, primary or winding 1 (WDGl) input currents to the relayare lA, IB, and Ic, and secondary or winding 2 (WDG2) currents are lAC, IBA, and ICB-

In order to provide correct compensation, the relay phase shifts WDG 1 currents to coincide withthe WDG2 delta currents: Once WDGI currents are scaled by the TAP setting, Ic is subtractedfrom lA, IA is subtracted from IB, and IB is subtracted from Ic to provide lAC, IBA, and ICB- Each

current is reduced by a factor of -J3 to equal the original line current magnitude.

The relay provides this compensation for all wye-wye connected CTs associated with any wye-deltacombination or wye-wye connected power transformer. This is an important note from.a testiP.gperspective in that any" single-phaseinjection of cl!!I.~uLintp thY....IDeside of a power transformer

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TRCON CTCON A BSetting Setting

yy YY -J3 -J3YDAC YY -J3 1

YDAB YY -J3 1

DABY YY 1 -J3DACY YY 1 -J3

All other connections 1 1

Table 1: Current Connection Compensation for Testing

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3.3 RelayCurrent Taps

The relay will automatically calculate current taps, TAPI and TAP2 provided setting MY A:;t OFF.Tap settings are limited to a range of O.I (IN) to 32(IN) and the tap ratio TAPmaxiTAPmin:::;4.S. INis the nominal current rating of the relay and is equal to either IA or SA.

Tap settings can be manually calculated using the formulae

TAPl = (MVA)(IOOO)(Cl)(,/3 )(VWDGI)(CTR1)

TAP2 = (MVA)(lOOO)(C2)(,/3 )(VWDG2)(CTR2)

Cl, C2 = 1 for all wye-connected CTs

ci, C2 = ,/3 for all delta-connected CTs

Refer to Table 4.1, TRCON, CTCON, and Current Compensation Factors for 2 WindingTransformer Banks, in the SEL 587 manual.

3.4 PercentageRestrainedDifferential Element

Refer to Figure 3: Percentage Restraint Differential Characteristic

Restrained, differential operation of the relay is based on a composite characteristic made up ofthree "regions". These regions are created by four different settings:

• 087P (restrained element operating current pickup set in per unit of TAP)

• SLPl (restraint slope l, set in percentage)

" IRS 1 (restraint current, slope 1 limit, set in per unit of TAP)

fI SLP2 (restraint slope 2, set in percentage)

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Number 42.87.731-8

Subject SEL 587SEL 587 Relay


lOP(PerUnit)

087P

I087P

x 100

IIRS1 IRT

(Per Unit).:SLP1

-:

Figure 3 Percentage ~estraint Differential Characteristic

3.4.1 087P: ope-(l-f;-1\ 1J9 cv~(l$'~ ?)G\('.\ - v f .

The 087P setting is the "region 1" operate point of the relay. Pickup at this setting occurs forrestraint currents less than or equal to (087P/SLP1) x 100 - the boundary current between regions1 and 2.

The 087P setting must yield an operating current greater than O.l(IN), when multiplied by thesmaller of TAP 1 and TAP2. (IN is the nominal current rating of the relay and is equal to either 1Aor SA).

Therefore, region 1 operation is given by

lOP = 087P087P

forlRT:S; SLP1 X 100

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Subject SEL 587Titie: SEL 587 Relay


3.4.2/l'1Pl&r.-U-" S1Sl ~ ~~oIQ -ro ~tJ-l PMhf' l(Z.,\f0N~ \')-j+- Tb (,"\~e C~ vo"/0 ~

SLP1 l L.TC \/\'til.-I,1"IIl,:)NL0! loOt",) r.:.e. ~~C;I-\' \-¥lVt-T UN'OI\l"i-l)

Setting SLP1 provides the first restraint slope percentage of the relay and defines "region 2"operation. This is a linear characteristic that can be extrapolated through the origin of the lOP vs.IRT graph. Therefore, basic linear algebra results in the line equation

'I \ I i. I ' I

J (SLP1)(IRT)IOP=

100087P

for --x 100 ::; IRT ::; IRS1 settingSLP1

3.4.3 IRS1 C1'4f'IO'lvI---( S"bT e. ?, 9tl -tp"p)

The IRS1 setting is the IRT limit of the slope 1 setting and is the boundary current between theSLP1 characteristic (region 2) and the SLP2 characteristic (region 3).

IfSLP2 *- OFF, IRS 1 must be set greater than (l25)(087P/~LPl), i.e. IRSI must be set at aminimum of 125% of the IRT intersection point of087P setting and the SLP1 characteristic.

The IRS 1 setting is not used if SLP2 = OFF

3.4.4 SLP2 [\VI e/~,,/ Sti ~ ::yo -b~v/", w ~a,~ ~S!,\ ~\ ~t?\rJ~ P--l\:.. T't>c T S.i7"Tv Q...A-1l<> rJ etZ..-v e..~)

The setting, SLP2, provides the second restraint slope percentage of the relay and defines "region3" operation. This is a linear characteristic offset from the origin of the lOP vs. IRT graph.Therefore, basic linear algebra results in the line e~ - 'b 'f\~c.arrt-J ~ <:~-Q ~ 2-

/: (SLP2)(IRT) - ~1) /lOP = for IRT ~ IRS1

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3.4.5 Determining Winding Input Currents for Testing

As outlined above, the typical restrained differential operating characteristic has three distinct"regions".

. 087Pe Region 1 occurs for IRT::;--X 100 and lOP = 087P

SLP1

. 087P (SLP1)(lRT)• Region 2 occurs for --x 100 ::; IRT ::; IRS1 setting and lOP =

SLP1 100

(SLP2)(IRT) - (IRS1)(SLP2 - SLP1)G Region 3 occurs for IRT ~ IRS 1and lOP = 100

The relay requires testing at four distinct points to verify the various regions of the differentialcharacteristic. These points have been arbitrarily chosen at

1) 95% of the region 1 boundary.

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Number 42.87.731-8



2) 125% of the region 1 boundary.

3) 95% of the IRS 1 setting.

4) 150% of the IRSI setting.

3.4.5.1 Case 1: 95% of the Region 1 Boundary (j:.~l)'-SI,.~iJ~(~ ~)

(

087P) 'iD(I;;:-oca7p::r 1-'0.IRT =(.95) SLPI (100) lOP = 087P

~1(\\1- ~and IRT = (lIWII + IIW21)12 and lOP = IIWII - IIW21

therefore IIWII = (.95)(087P) (200) - !IW2! therefore IIW21 = IIWII- 087PSLP 1 "'" ~----..-J

~--- -substituting for IIW21

(087P)IIWII = (.95) SLPI (200) - !1,wI!+ 087P

J = 087P (~+!)SLPI 2

and IIW21 = IIWII - 087P

/ = 087P (~-!)SLPI 2

where IWI and IW2 are the per unit input currents into winding 1 and 2 respectively.

Therefore, actual input winding currents for winding 1 (IWDGI) and winding 2 (IWDG2) on asingle phase basis are

and

(95 1)IWDGI = 087P --+- x TAP 1 x A (where A is from Table 1)

SLPI 2 ..

(95 1)IWDG2 = 087P SLPI -"2 x TAP2 x B (where B is from Table 1)

3.4.5.2 Case 2: 125% of the Region 1 Boundary

./ IRT = (1.+5{ ~~;~}100) / lOP = (IRT)(SLPI) r

100\

IRT = (lIWII + IIW21)/2 and lOP = IIWII -IIW21and

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(087P)IIWll= (1.25) - (200) - IIW21SLPI

therefore IIW21= IIW11 _ (IRT)(SLPl)100

therefore

substituting for IIW21 substituting for IRT

= (1.2S)(087P)(200) - IIWll+1.2S(087P)SLPI .

(100 1)

= 1.2S(087P) SLPI +'2

and IIW21= IIWll - 1.25(087P)

(100 1)

= 1.25(087P) SLPl-'2

IIW21= IIWll - 1.2S(087P)IIWII

where IWl and IW2 are the per unit input currents into winding 1 and 2 respectively.

Therefore, actual input winding currents for winding 1 (IWDGl) and winding 2 (IWDG2) on asingle phase basis are

(100 1) .IWDGI = 1.25(087P) ---f.- x TAP 1 x A (A 1S from Table 1)

SLPI 2

and (100 1) .IWDG2 = 1.25(087P) ---- x TAP2 x B (B IS from Table 1)

SLPI 2

3.4.5.3 Case 3: 95% of IRS1 Setting

IRT = .95(IRSl) lOP = (IRT{ SLPl)100

and IRT = (lIWll + IIW21)/2 and lOP = IIWII-IIW21

(SLPl)therefore IIWll= (2)(.9S)(IRSl) -IIW21 therefore IIW21 = IIWll - (IRT) 100

substituting for IIW21 substituting for IRT/ '

IIWll= (2)(.95)(IRSl)-IIWll+(.95{Sl~~1}IRSl) IIW21 = IIWll- (.95)(Sl~~1)(IRSl)

= .9S(IRSl)(1 + SLPl)200

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and IIW21=IIW11- (.95)(SLPl)(IRS1)100

( SLP1)= .95(IRS1) 1--200

where IW1 and IW2 are the per unit input currents into winding 1 and 2 respectively.

Therefore, actual input winding currents for winding 1 (IWDG1) and winding 2 (IWDG2) on asingle phase basis are

IWDGI = .95(IRS1)(1+ SLP1) x TAP 1 x A (A is from Table 1) /'200

and IWDG2 = .95(IRSl{l- S~:al) x TAP2 x B (B is from Table 1) ../

3.4.5.4 Case 4: 150% of IRS1 Setting

IRT = 1.5(IRSl)SLP2(IRT) - IRS1(SLP2-SLPl)

lOP =100

and IRT = (lIWll + IIW21)/2 and lOP = IIWll - IIW21

SLP2(IRT) - IRSl(SLP2- SLPl)therefore IIW21=IIWll- 100

substituting for IRT1.5(IRS1)SLP2- IRS1(SLP2-SLPl)

IW2 = IIW11- -----1-00-"------'-

therefore IIW11=(2)(1.5)(IRS1) -IIW21

substituting for IIW21

and

l.5(IRS I)SLP2 - IRS1(SLP2- SLPl)IWI = (2)(l.S)(IRSl) -IIWll + 100

(SLPI + (.5)SLP2)

= 1.5(IRSl) 1+ (1.5)(200)

1.S(IRS1)SLP2- IRSI(SLP2 -SLP1)IIW21=IIW11- 100

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_ ( )( SLPI + (.5)SLP2)- 15 IRS 1 1- ( )( ), 1.5 200

where IWI and IW2 are the per unit input currents into winding 1 and 2 respectively.

Therefore, actual input winding currents for winding 1 (IWDG1) and winding 2 (IWDG2) on asingle phase basis are

and

(SLPI + (.5)SLP2)

IWDGI = I.S(IRS1) 1+ (1.5)(200) x TAP 1 x A

(SLPI + (.S)SLP2)

IWDG2= I.S(IRS1) 1- (1.5)(200) xTAP2xB

A & B are multipliers from Tabl~ 1.

3.4.6 Harmonic Blocking

The percentage-restrained differential element can be blocked by either second and/or fifthharmonic using the PCT2 and/or PCT5 settings, respectively. Set these settings to "OFF" ifblocking is not required.

Transformer magnetizing inrush currerit contains a significant amount of second harmonic. If theratio of second harmonic to fundamental current (IF2/IF1) is greater than PCT2 setting, blockingoccurs.

Transformer overexcitation produces odd order harmonics. A fifth harmonic componentexceeding PCTS setting enables restrained-differential blocking.

Harmonic blocking can be either "Independent" or "Common". Independent Harmonic Blocking(IHBL = Y) blocks differential operation of a particular phase if the harmonic content of thatphase exceeds the pickup level. Common Harmonic Blocking (IHBL = N) blocks all differentialelements if anyone phase exceeds the pickup level.

3.5 Instantaneous Unrestrained Differential Element ~'):) I \)

The instantaneous unrestrained differential element responds to fundamental frequency only and isnot affected by SLP1, SLP2, IRS1, PCT2, PCT5, or IHBL settings.

4.0 SELogic Control Equations

SELogic equations are set from Access Level 2 using the SET L command. There are ten logicequations:

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f--~----~--~------~--------I


Subject SEL 587TiUe: SEL 587 Relay


• two variable equations (X and Y)

e three trip equations; MTUI (TRPl), MTU2 (TRP2), and MTU3 (TRP3)

e one event trigger equation (MER)

It four output equations (OUTl, OUT2, OUT3, and OUT4)

Eligible relay word bits for each equation are listed in Table 5.3 of the relay manual. Certainrestrictions apply to building these equations. These are outlined in section 5 of the relay manual.

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Documents

SEL-587 Training Notes