Capacitor/Filter-ProtectionRelay CPR 04

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Capacitor/Filterprotection Relay CPR 04

Application

The CPR 04 provides compre-hensive protection for thecapacitive, inductive and resis-tive elements of three phasemedium and high voltageshunt capacitor banks and har-monic filter circuits.The capacitor banks may havea single star, double star, deltaor „H“ configuration, withinternally fused, externallyfused or unfused capacitor units.

A high performanceprotection relay for capacitor banks

and harmonic filter circuits

• Operating mode software selectable(NORMAL / H-BRIDGE)

• RS232 serial data port atthe front

• Software selectable RS232or RS485 serial data port at the rear

• Time stamping function for trip history and setting menu

Introduction

The Trench CPR 04 is a com-prehensive, numeric protectionrelay, featuring:

• Compact draw-out design

• Panel or 19 inch rack mounting

• Four software configurable measuring elements

• Five configurable output relays

• One self-supervision output relay

• User configurable, to cater for a wide range of relaysettings

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NORMAL MODE - Protective functions

Peak repetitiveovervoltage protection

For each phase, CPR 04 deter-mines the peak repetitive capa-citor voltage using advancedDigital Signal Processor (DSP)techniques, by integrating themeasured line current wave-form, to give a signal represen-ting the voltage waveform ap-plied to the capacitor bank.The peak repetitive voltage ofthis signal is then extracted,and compared to adjustablethresholds. For calculated peakrepetitive voltages above thethresholds, a starter signal isoutput, and the inverse timeANSI capacitor temporary over-voltage withstand curve respec-tively adjustable definite timersdefine the time before trip sig-nals are output.

Thermal overcurrentprotection

For each phase, CPR 04 pro-tects a capacitor bank / har-monic filter circuit from excessthermal current stressing, bymodelling the thermal responseof the circuit to the rms hea-ting current, Irms. A secondorder thermal model and asso-ciated adjustable heating / coo-ling time constant is then usedto continuously calculate thethermal current response lth, tothe rms heating current. Ith is

compared to adjustable thres-holds, which are linked to adju-stable definite timers. Trip sig-nals are output, if the associa-ted threshold is exceeded forthe definite time set.

Star pointunbalance protection

CPR 04 measures the star pointunbalance current, and calcula-tes the fundamental frequencycomponent, Iub.This can then be compensated,in magnitude and phase angleto zero, to enable detection offurther changes, in bothmagnitude and phase angle,(∅Iub). The magnitude is ameasure of the change in capa-citance in any leg of a doublestar capacitor bank arrange-ment, whereas the phase angleindicates the leg in which thechange in capacitance has oc-curred.The magnitude of (∅)Iub is con-tinuously compared with adju-stable thresholds, each with anadjustable definite timer.Trip signals are output, if theassociated thresholds are ex-ceeded for the definite times set.

Line currentunbalance protection

The monitoring of line currentunbalance provides a means of

detecting changes in impedanceresulting from failures andfaults within the capacitorbank / harmonic filter circuit.These faults or failures invari-ably result in an unbalance inthe fundamental frequencycomponent of the line currents.

CPR 04 calculates the funda-mental frequency line currentunbalance, Ilub, from the threephase line currents. Ilub is con-tinuously compared with adju-stable thresholds each with anadjustable definite timer. Tripsignals are output if the asso-ciated thresholds are exceededfor the definite times set.

The sensitivity of line currentunbalance protection islimited by the effect of supplyvoltage unbalance on the linecurrents. Nevertheless, line cur-rent unbalance protection isuseful as back-up protection tostar point unbalance protection.

Earth fault protection

CPR 04 calculates the funda-mental frequency earth faultcurrent, Io , as the magnitudeof the vector sum of the threephase line currents. Io is com-pared with adjustable thres-holds each with an adjustabledefinite timer. Trip signals areoutput, if the associated thres-holds are exceeded for the de-finite times set.

Fundamental frequencyovercurrent protection

For each phase, CPR 04 calcu-lates the fundamental frequen-cy component, I1 , of the linecurrent. I1 is continuously com-pared with adjustable thres-holds each with an adjustabledefinite timer. Trip signals areoutput, if the associated thres-holds are exceeded for the de-finite times set.

RMS -overcurrent protection

For each phase, CPR 04 calcu-lates the rms current, Irms ,(fundamental + harmonics upto the 50th). Irms is continuouslycompared with adjustablethresholds each with an adju-stable definite timer.Trip signals are output if theassociated thresholds are ex-ceeded for the definite times set.

Undercurrent protection

For each phase, CPR 04 calcu-lates I1 , the fundamental fre-quency component of the linecurrent. I1 is continuouslycompared with an adjustableundercurrent threshold, I1<,with an associated adjustabledefinite timer. With the capaci-torbank / harmonic filter circuitbreaker on, if the mains powersupply fails, as indicated by adrop in I1 below I1< for longerthan the definite time set, thenthe undercurrent trip signalis output.

Breaker fail protection

If I1 remains above the under-current threshold for longerthan the adjustable definitetime after the breaker switchesoff, or after a trip output signalhas been given by CPR 04,then this indicates a failure ofthe breaker, and the breakerfail signal is output. This signalcan be used trip to an up-stre-am breaker.

Capacitor bankdischarge timer

CPR 04 provides the necessarylogic, and a breaker inhibitoutput signal, Bena, to inhibitthe re-energization of thecapacitor bank / harmonic filtercircuit breaker, for an

adjustable definite time sincede-energization

Event Trip

CPR 04 provides the necessarylogic, to trip any of the outputrelays via a change in the statusof the digital input.

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NORMAL MODE - Protective functions

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„H“ configurationcapacitor bankunbalance protection

In an alternative user-configu-rable operating mode, CPR 04provides fundamental frequency„H“ configuration capacitorbank unbalance protectiononly. This provides sensitive un-balance protection indepen-dently for each phase of a ca-pacitor bank.

For each phase the CPR04 calcu-lates the fundamental compo-nent of the measured unbalancecurrent. The natural unbalanceof each phase can then be com-pensated in amplitude and phaseangle, to detect subsequentchanges. (∅a/b/c lub)The unbalance current (∅)a/b/club is then compared to adju-stable thresholds, each with anadjustable timer. Trip signalsare output, if the thresholdsare exceeded for the definitetimes set.

H-BRIDGE MODE - Protective function

Measuring elements

Four current measuring elementsare provided within CPR 04.The nominal current (1A/5A)can be set in the menu.

Relay outputs

CPR 04 has six output relays.

The functionality of outputrelays 1 to 5 is user configura-ble. The user may program therelays to be manual or self-resetting, and to be normallyenergized or de-energizedduring the power-up healthycondition. In addition, the usermay direct any of the binaryoutput signals of the protectivefunctions to output relays 1 to 5.

Output relay 6 is the self-super-vision relay for CPR 04, and isenergized in the power-up,normal condition, and de-ener-gizes on loss of auxiliary powersupply, or on failure of CPR 04internal power supply, micro-processor hardware, softwareor memory.

Contact forms

Output relays 1 to 6 each haveone change-over contact. Asdefault, all output relays aresupplied with the normallyopen (relay de-energized)contacts wired to the terminal

Relay design

block. However, the user caneasily change the contacts ofthe output relays to be as re-quired by the application.

Auxiliary power supply

A high efficiency, low loss, widerange AC/DC auxiliary powersupply is provided within CPR 04.Special care has been taken tominimize the overall standingload of CPR 04 on the DC stati-on batteries or AC busbar vol-tage supply.

The CPR 04 nominal auxiliarypower supply voltage is 30 -250 V ac/dc. For the operativerange see technical specificati-ons, page 10.

Time stamping

CPR04 features a built in realtime clock which allows to timeand date stamp trip events aswell as modifications to set-tings and status registers. Theclock is backed up by a main-tenance free supercap.

Serial data port

CPR 04 is provided with aRS232 frontport and a soft-wareselectable RS232 or RS485serial data port at the rear fordata communications betweenan intelligent host device andthe protection relay.

The RS232 port at the frontalso allows for future firmwareupgrades as additional func-tions and features might beadded.

The serial data port can beused for the following purposes:

• Downloading of a set-up fileto a CPR 04.

• Uploading from a CPR 04 of the set-up file currentlyactive within the relay.

• Uploading from a CPR 04 of any error codes, or alarm and trip annunciationmessages.

• The uploading from a CPR 04of various instantaneousparameters, measured andcalculated by the relayduring normal operation.

• Interconnection into a SCADA system usingMODBUS RTU protocol

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Interactive configuration of the protection relay

• During testing:Interactive self testing of the protection relay

• After failure:Annunciation of any protec-tion relay hardware, soft-ware or memory failures de-tected during self-testing of the protection, by display of the relevant error codes.

Test facilities

While CPR 04 is in service, itcontinuously performs variousself-testing functions, and ifany errors or failures are detec-ted, the corresponding errorcode(s) will be displayed, andthe self-supervision outputrelay will de-energize, to signalthe malfunction. These self-tests include tests of the micro-processor, RAM, ROM andEEPROM.

In addition, a further set ofhardware diagnostic tests maybe performed on the protec-tion relay by the user, to testand check the functionality ofthe measurement offsets forelements 1 to 4, the digitalinput, relay outputs, keypad,LCD display and LEDs.

Relay design

LED indicators

Three LED indicators are provi-ded on the front panel of CPR04, as follows:

• Green LED: This indicates that the auxili-ary power supply is on, and the self-supervision output relay is energized, indicating that the protection relay is healthy.

• Yellow LED:This indicates that one (or more) of the „starter“binary outputs signals of a protection function is (are) atlogic 1 (high), and that the protection relay may trip if the condition persists.

• Red LED:This indicates that a tripcondition has occurred that has not yet been reset and / or acknowledged.

LCD display

A two line, 16 character, fullalpha-numeric, back-lit, LiquidCrystal Display (LCD) is provi-ded on the front panel of CPR04 for the following purposes:

• During normal operation:The display of various mea-sured and calculatedparameters, together with

the low-set thresholdsassociated with theseparameters.

• After a relay trip condition:Annunciation of all the fault conditions after a trip, inclu-ding the value of the fault currents and voltages at the instant of trip, and the relay trip time after occurance of the fault condition.

• During relay configuration and normal operation: Display of the current and voltage thresholds and timersettings for each element, anddisplay of each output relay configuration and check-sum.

• During relay configuration:

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Housing and terminals

CPR 04 is housed in a draw-outchassis within a fixed case. Thishousing is particularly suitablefor both flush mounting and19 inch rack mounting. Thecase is designed for indoor usein tropical climate and is desi-gned to withstand shock, vi-bration and the ingress of dustand moisture.A terminal block, with 28 re-cessed terminals, is provided onthe fixed case. Standard screwterminals, or fast-on connectors,can be used on the terminalblock, for the external connec-tions to the protection relay.

Withdrawing the protectionrelay module automaticallyshort circuits the current trans-former terminals.

Keypad

A five button key-pad is provi-ded on the front panel of CPR04 for the following purposes:

• Interactive configuration ofthe protection relay

• Acknowledgment andresetting of trip conditions

• Hardware diagnostic testing

PC basedsoftware package

A Windows based softwarepackage is available for CPR 04to exploit its communicationfacilities. This software packageenables the user to create, edit,save, open and print anynumber of CPR 04 set-up fileson a PC, and to download orupload a set-up file to or froma CPR 04, either directly or viaMODEM. In addition, all theother facilities and functions ofthe serial data port, as detailedabove, can be exploited usingthis software package.

Digital input

CPR 04 is provided with anoptically isolated, binary(on / off), voltage input channel.Any voltage from 30 - 250 VAC/DC applied to this inputchannel will signal that theinput is active.

The functionality of the digitalinput is depending on thesetting in the relevant menu.

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Relay design

General characteristics

Applicable standard IEC 60255 and EN 50263Operating temperature range -10 to +55 °C to IEC 60068-2-2Storage temperature range -20 to +70 °C to IEC 60068-2-2Humidity 4 days, 95% RH,

with temperature cycled between +25OC and + 45OC,to IEC 60068-2-3

Enclosure degree of protection IP50 to IEC 60529Shock and bump Shock: 15g, 3 pulses per direction, per axis. (total 18 times).

Bump : 10g, 1000 pulses per direction, per axis (total 6000 times).To IEC 60255-21-2

Vibration 9,8ms-2 (1g) constant frequency from 10 to 150 Hz per axis.To IEC 60255-21-1

Power frequency voltage withstand 2 kV rms 50 Hz for 1 minute, from all terminals to case (earth),and between terminals of independent circuits.1,5 kV rms across open contacts of output relays.To IEC 60255-5

Impulse voltage withstand 5 kV peak, 1,2/50 µs waveshape, 0,5 J energy content,10 shots in each polarity, between all terminals and case (earth), and between terminals of independent circuits.To IEC 60255-5

Insulation resistance 50 MΩ minimum at 500 VDC, to IEC 60255-5Immunity to high frequency 2,5 kV peak between independent circuits, and to case (earth).disturbances 1 kV peak across terminals of the same circuit.(1MHz burst disturbance test) To IEC 60255-22-1Immunity to electrostatic 8 kV discharge in airdischarges 6 kV point contact discharge(Electrostatic discharge test) To IEC 60255-22-2 and EN 50263Immunity to fast transient bursts 4kV supply lines / 2kV input & output lines /(Fast transient burst test) 1kV communication lines

To IEC 60255-22-4 and EN 50263Immunity to high frequency 10 V / m, 100% PM, at 900 MHzelectromagnetic fields 10 V, 80% AM, from 150 kHz to 80 MHz as well as

10 V / m, 80% AM, from 80 MHz to 1000 MHz, to EN 50263Immunity to surge voltages 2kV peak common / 1kV peak differential

To EN 61000-4-5 and EN 50263Immunity to voltage interruptions 230 VAC – 100% interruption – 200ms

110 VDC – 100% interruption – 50msTo EN61000-4-11

Harmonics and flicker of main current To EN 61000-3-2Conducted emissions To EN 50263, from 150 kHz to 30 MHz.Radiated emissions To EN 50263, from 30 MHz to 1000 MHz.Nett Mass 3 kgOverall dimensions 103(w) x 177(h) x 248(d)

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Technical specifications

Measuring Quantity 4elements Nominal rated current, In 1A or 5A selectable in the software

Continuous current 15AShort time current 300A for 1sBurden <40mΩAccuracy of measurement +/- 2% of nominal rated current

Auxiliary power Nominal rated voltage, Vx 30 – 250V AC / DCsupply Operative range AC / DC 40 - 250V AC / 30 - 300V DC

Burden with DC supply <14W with all relays and back-light ONBurden with AC supply <24VA with all relays and back-light ON

Output relays Quantity Alarm / trip relays: 5 Self-supervision relay: 1Contact form (per relay) 1 – changeover contact (form C), user configurable

as N/O or N/CLoad Resistive load: Inductive load:

(cos � = 1) (cos � = 0,4 L/R = 7 ms)K1 Rated load 5A at 250 VAC 3,5A at 250 VAC

1A at 220 VDC 0,8A at 220 VDC3A at 110 VDC 2A at 110 VDC5A at 48 VDC 4A at 48 VDC

Max. operating voltage 380VAC, 250 VDCK2, K3, K4, K5, K6 Rated load 5A at 250 VAC 3,5A at 250 VAC

5A at 30 VDC 2,5A at 30 VDCRated carry current 5AMax. operating voltage 380VAC, 125 VDCMin. permissible load 100mA at 5 VDC

Digital input Quantity 1channel Function Breaker on; Remote reset; Event trip

Isolation Optically isolatedType 30 – 250V AC / DC voltage input

Pushbuttons Function >, <, ^, , and ACCEPT (red)Type Miniature spring loaded manual pushbuttons

Display Type Back-lit Liquid Crystal Display (LCD),with full alpha-numeric character set

Screen Size 16 character x 2 lineCharacter height 4mm

Indicators Type Light Emitting Diodes (LEDs)Function Green : POWER ON / HEALTHY

Yellow : START (ALARM)Red : TRIP

Serial data port Quantity 2Isolation Optically isolatedFrontport type RS232 via DB9 socketRearport type RS232 or RS485 – selectable in the softwareBaudrate (kBd) 2.4 up to 115.2 for each port seperatly selectable

Real Time Clock Functionality Date; Weekday; HH:MM:SSAccuracy +/- 30 s per monthBackup Supercap (>14 days without power)

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Block diagram

Änderungen vorbehalten04.09

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