Arcteq AQ-T256 User manual

AQ-T256

Transformer protection IED

Instruction manual

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Table of contents

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1. Manual revision notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.1. Version 2 revision notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.2. Version 1 revisionnotes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4. IED user interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.1. Panel structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.1.1. AQ 250 series local panel structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.2. User level password conguration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5. Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.1. Functions included in AQ-T256 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.2. Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.2.1. Current measurement and scaling in differential application . . . . . . . . . . . . . . . . . .

5.2.2. Frequency tracking and scaling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.3. General menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.4. Protection functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.4.1. General properties of a protection function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.4.2. Non-directional overcurrent I> (50/51) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.4.3. Non-directional earth fault I0> (50N/51N) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.4.4. Current unbalance I2> (46) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.4.5. Harmonic overcurrent Ih> (50H/51H/68H) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.4.6. Circuit breaker failure protection CBFP (50BF) . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.4.7. Restricted earth fault / cable end differential (REF) I0D> (87N) . . . . . . . . . . . . . . . .

5.4.8. Transformer status monitoring (TRF) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.4.9. Transformer thermal overload protection TT> (49TR) . . . . . . . . . . . . . . . . . . . . . . .

5.4.10. Transformer differential Idb> Idi> I0dhv> I0dLv> (87T,87N) . . . . . . . . . . . . . . . . . .

5.4.11. Resistance temperature detectors (Modbus IO) (RTD) (49T) . . . . . . . . . . . . . . .

5.4.12. Arc fault protection IArc>/I0Arc>(50Arc/50NArc) . . . . . . . . . . . . . . . . . . . . . . . .

5.4.13. Programmable stage PGx >/< (99) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.5. Control functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.5.1. Setting group selection (SGS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.5.2. Object control and monitoring (OBJ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.5.3. Indicator object monitoring (CIN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.5.4. mA Output control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.6. Monitoring functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.6.1. Current transformer supervision (CTS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.6.2. Disturbance recorder (DR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.6.3. Measurement recorder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.6.4. Circuit breaker wear-monitor (CBW) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.6.5. Total harmonic distortion monitor (THD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.6.6. Measurement value recorder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6. System integration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6.1. Communication protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6.1.1. NTP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6.1.2. ModbusTCP and ModbusRTU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6.1.3. ModbusIO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6.1.4. IEC 61850 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6.1.5. GOOSE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6.1.6. IEC 103 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6.1.7. DNP3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6.1.8. IEC 101/104 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6.1.9. SPA protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6.2. General IO analog fault registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6.3. Real time measurements to communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7. Applications and connection examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7.1. Connections AQ-T256 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

AQ-T256

Instruction manual

Version: 2.00

1 © Arcteq Relays Ltd

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7.2. Example transformer application connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7.3. Trip circuit supervision (95) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8. Construction and installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8.1. Construction and installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8.2. CPU, IO and Power supply module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8.3. Current measurement module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8.4. Binary input module (DI8) (option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8.5. Binary output module (DO5) (option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8.6. Arc protection module (option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8.7. RTD & mA input module (option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8.8. Serial RS232 communication module (option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8.9. LC100 Ethernet communication module (option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8.10. mAout & mAinput module (option) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8.11. Installation dimensioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9. Technical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9.1. Hardware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9.1.1. Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9.1.1.1. Current measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9.1.1.2. Frequency measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9.1.2. CPU & Power supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9.1.2.1. Auxiliary voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9.1.2.2. CPU communication ports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9.1.2.3. CPU Binary inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9.1.2.4. CPU Binary outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9.1.3. Option cards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9.1.3.1. Binaryinput module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9.1.3.2. Binary output module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9.1.3.3. Arc protection module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9.1.3.4. mAout & mAin module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9.1.3.5. RTD & mA input module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9.1.3.6. RS232 & Serial ber communication module . . . . . . . . . . . . . . . . . . . . . .

9.1.3.7. Double LC100Mb Ethernet module(Redundant) . . . . . . . . . . . . . . . . . . .

9.1.4. Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9.2. Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9.2.1. Protection functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9.2.1.1. Non-directional overcurrent (50/51) I> . . . . . . . . . . . . . . . . . . . . . . . . . . .

9.2.1.2. Non-directional earth fault (50N/51N) I0> . . . . . . . . . . . . . . . . . . . . . . . .

9.2.1.3. Current unbalance (46/46R/46L) I2> . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9.2.1.4. Harmonic overcurrent (50H/51H, 68) Ih> . . . . . . . . . . . . . . . . . . . . . . . .

9.2.1.5. Circuit breaker failure protection (50BF/52BF) CBFP . . . . . . . . . . . . . . .

9.2.1.6. Restricted earth fault / Cable end differential (87N) Iod> . . . . . . . . . . . . .

9.2.1.7. Transformer thermal overload (49T) T> . . . . . . . . . . . . . . . . . . . . . . . . . .

9.2.1.8. Resistance temperature detector alarm (49RTD) T> . . . . . . . . . . . . . . . .

9.2.1.9. Transformer monitoring function (TRF) . . . . . . . . . . . . . . . . . . . . . . . . . . .

9.2.1.10. Transformer differential (87T,87R) Idb>, Idi>,HV Iod>, LV Iod> . . . . . . .

9.2.1.11. Arc protection (50ARC/50NARC) IARC> I0ARC> (option) . . . . . . . . . . .

9.2.2. Control functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9.2.2.1. Setting group selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9.2.2.2. Object control (OBJ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9.2.3. Monitoring functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9.2.3.1. Current transformer supervision (CTS) . . . . . . . . . . . . . . . . . . . . . . . . . .

9.2.3.2. Disturbance recorder (DR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9.2.3.3. Circuit breaker wear monitor (CBW) . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9.2.3.4. Total harmonic distortion (THD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9.3. Tests and environmental . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

10. Ordering information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

11. Contact and reference information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

AQ-T256

Instruction manual

Version: 2.00

Disclaimer

Please read these instructions carefully before using the equipment or taking any other actions with

respect to the equipment. Only trained and qualied persons are allowed to perform installation,

operation, service or maintenance of the equipment. Such qualied persons have the responsibility to

take all appropriate measures, including e.g. use of authentication, encryption, anti-virus programs,

safe switching programs etc. necessary to ensure a safe and secure environment and usability of the

equipment. The warranty granted to the equipment remains in force only provided that the instructions

contained in this document have been strictly complied with.

Nothing contained in this document shall increase the liability or extend the warranty obligations of the

manufacturer Arcteq Relays Ltd. The manufacturer expressly disclaims any and all liability for any

damages and/or losses caused due to a failure to comply with the instructions contained herein or

caused by persons who do not full the aforementioned requirements. Furthermore, the manufacturer

shall not be liable for possible errors in this document. 

Please note that you must always comply with applicable local legislation and regulations. The

manufacturer gives no warranties that the content of this document is in all respects in line with local

laws and regulations and assumes no liability for such possible deviations.

You are advised to notify the manufacturer in case you become aware of any errors in this document or

of defects in the equipment.

The manufacturer reserves the right to update or amend this document at any time.

AQ-T256

Instruction manual

Version: 2.00

3 © Arcteq Relays Ltd

Copyright

AQ-T256

Instruction manual

Version: 2.00

1. Manual revision notes

1.1. Version 2 revision notes

Revision 2.00

Date 6.6.2019

Changes

- New more consistent look.

- Improved descriptions generally in many chapters.

- Improved readability of a lot of drawings and images.

- Updated protections included included in every IED manual.

- Every protection IED type now has connection drawing, application example drawingwith function block diagram

and application example with wiring.

- Added current measurement side selection description to functions with such feature.

- Added General-menu description.

1.2. Version 1 revisionnotes

Revision 1.00

Date 13.4.2016

Changes - The rst revision for AQ-T256, T257 and T259 IEDs.

Revision 1.01

Date 10.2.2017

Changes

- Order code updated

- Added programmable stage description

Revision 1.02

Date 9.1.2018

Changes

- Measurement value recorder description

- ZCT connection added to current measurement description

- Internal harmonics blocking to I>,I0> function descriptions

- Non-standard delay curves added

- Event lists revised on several functions

- RTD&mA card description improvements

- Ring-lug CT card option description added

- New U> and U< function measurement modes documented

- Order code revised

Revision 1.03

Date 14.8.2018

Changes

- Added mA output option card description and ordercode

- Added HMI display technical data

AQ-T256

Instruction manual

Version: 2.00

5 © Arcteq Relays Ltd

2. Abbreviations

CB – Circuit breaker

CBFP – Circuit breaker failure protection

CT – Current transformer

CPU – Central processing unit

EMC – Electromagnetic compatibility

HMI – Human machine interface

HW – Hardware

IED – Intelligent electronic device

IO – Input output 

LED – Light emitting diode

LV – Low voltage

MV – Medium voltage

NC – Normally closed

NO – Normally open

RMS – Root mean square

SF – System failure

TMS – Time multiplier setting

TRMS – True root mean square

VAC – Voltage alternating current

VDC – Voltage direct current

SW – Software

uP - Microprocessor

AQ-T256

Instruction manual

Version: 2.00

3. General

AQ-T256 Transformer Protection IEDisa members of the AQ-200 product line. The AQ-200 protection

product line in respect of hardware and software is a modular concept. The hardware modules are

assembled and congured according to the application IO requirements and the software determines

the available functions. This manual describes the specic applications of the AQ-T256Transformer

Protection IEDs. For other AQ-200 series products please consult corresponding device manuals.

AQ-T256

Instruction manual

Version: 2.00

7 © Arcteq Relays Ltd

4. IED user interface

4.1. Panel structure

AQ 200 series IED user interface section is divided into hardware- and software user interface

sections. Software interface is divided into local panel conguration and programming by using

AQtivate 200 freeware software suite.

4.1.1. AQ 250 series local panel structure

AQ 200 series IED have multiple LEDs, control buttons, function buttons and local RJ-45 Ethernet port

for conguration on front as a default. On rear each unit is equipped with RS-485 serial interface and

RJ-45 Ethernet interface options as a standard. See list below.

Figure. 4.1.1. - 1. Local panel structure.

4 default LEDs for free conguration: Power, Error, Start and Trip.

16 freely congurable LEDs with programmable legend texts.

3 object control buttons: Choose the controllable object with Ctrl –button, control breaker with

0- and I push buttons.

L/R push button for local remote control.

7 Navigation buttons for IED local programming and a button for password activation.

12 freely congurable function buttons.

RJ-45 Ethernet port for IED conguration.

Used views are freely congurable with buttons for changing settings groups or controlling the relays

logic in general. Object status (Circuit breaker/Disconnector) can be displayed on the screen. All

measured and calculated values (currents, voltages, power, energy, frequency etc.) can be shown in

the screen.

AQ-T256

Instruction manual

Version: 2.00

4.2. User level password conguration

As a factory default IEDs do not have any user levels locked behind passwords. In order to activate

different user levels click the IED HMI lock button and set the desired passwords for different user

levels.

NOTE: Passwords can be set only at local HMI.

In the HMI the user level currently in use is indicated in the upper right corner with stars.

Different user levels and the indicators are:

SUPERUSER (***) = full access including congurations

CONFIGURATOR (**) = access to all settings

OPERATOR (*) = access to limited settings and control

USER ( - ) = view only

You can set a new password for the user level by selecting the key icon next to the user level. After this

you can lock the user level by pressing return key while the lock is selected. If you need to change the

password you can select the key icon again and give a new password. Please note that in order to do

this the user level must be unlocked.

The required access level required to change a parameter is indicated with star (*) symbol if such is

required. As a general rule the access levels are divided as follows:

User:

Can view any menus and settings but cannot change any settings nor operate breakers

or other equipment.

Operator:

Can view any menus and settings but cannot change any settings BUT can operate

breakers or other equipment.

Congurator:

Can change most settings like basic protection pick-up levels or time delays,

breaker control functions, signal descriptions etc. Can operate breakers or other equipment.

Super user:

Access to change any setting and can operate breakers or other equipment.

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Instruction manual

Version: 2.00

9 © Arcteq Relays Ltd

5. Functions

5.1. Functions included in AQ-T256

This chapter presents the functions of AQ-T256 Transformer Protection IED. AQ-T256includes

following functions and amounts of instances of the functions.

Table. 5.1. - 1. Protection functions of AQ-T256

Name IEC ANSI Description

NOC1

NOC2

NOC3

NOC4

I>

I>>

I>>>

I>>>>

50/51 Overcurrent protection (4 stages)

NEF1

NEF2

NEF3

NEF4

I0>

I0>>

I0>>>

I0>>>>

50N/51N Residual overcurrent protection (4 stages)

CUB1

CUB2

CUB3

CUB4

I2>

I2>>

I2>>>

I2>>>>

46/46R/46L

Negative sequence overcurrent / phase current reversal / unbalance protection (4

stages)

HOC1

HOC2

HOC3

HOC4

Ih>

Ih>>

Ih>>>

Ih>>>>

50h/51h/68h

Detection and blocking or tripping from selectable 2nd, 3rd, 4th, 5th, 7th, 9th, 11th,

13th, 15th, 17th, 19th harmonic. Phase currents and residual currents separate

stages. (4 stages)

CBF1 CBFP 50BF/52BF Breaker failure protection

DIF1

Idb>

Idi>

87T Transformer differential function. Biased and non-biased stages

REF1

REF2

I0d>

87N Low or high impedance restricted earth fault, cable end differential protection

TOLT1 TT> 49L Transformer thermal overload protection

TRF TRF - Transformer status monitoring function

RTD1 RTD 49T Resistance Temperature Detectors for temperature measurements

PGS1 PGx >/< 99 Programmable stage

ARC1 IArc>/I0Arc> 50Arc/50NArc Arc protection (Option)

Table. 5.1. - 2. Control functions of AQ-T256

Name IEC ANSI Description

SG - - Set group settings

OBJ - - Object control

Table. 5.1. - 3. Monitoring functions of AQ-T256

Name IEC ANSI Description

CTS - - Current transformer supervision

DR - - Disturbance recorder

MR - - Measurement recorder

CBW - - Circuit breaker wear monitor

THD - - Total harmonic distortion

VREC - - Measurement value recorder

AQ-T256

Instruction manual

Version: 2.00

5.2. Measurements

5.2.1. Current measurement and scaling in differential application

Current measurement module (CT-module) is used for measuring the currents from current

transformers and processing the measured currents to measurement database and for use of

measurement- and protection functions. For the measurements to be correct it is essential to

understand the concept of current measurements.

Figure. 5.2.1. - 2. Current measurement terminology

PRI: Primary current, the current which flows in the primary circuit and through primary side of the

current transformer.

SEC: Secondary current, the current which the current transformer transforms according to its ratios.

This current is measured by the protection IED.

NOM: Nominal primary current of the protected transformer. Nominal current differs on the HV and LV

side according to the transformer voltage ratio. Nominal current is calculated based on transformers

MVA and nominal voltage on each winding.

For the measurements to be correct it needs to be made sure that the measurement signals are

connected to correct inputs, current direction is connected correctly and the scaling is set correctly.

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Instruction manual

Version: 2.00

11 © Arcteq Relays Ltd

For scaling, the relay calculates scaling factors based onto the set CT primary, secondary and nominal

current values. Relay measures secondary current which in this case mean the current output from the

current transformer which is installed into the primary circuit of the application. In order the relay to

“know” primary and per unit values it needs to be told the current transformer rated primary and

secondary currents. In case of a power transformer the protected unit nominal current in both windings

is calculated based on given nominal power (MVA) and nominal voltage (V), only when the nominal

current is known the settings can be per unitized to apparatus nominal. By knowing the transformer

nominal current it makes the unit protection a lot easier and straight forward. In modern protection

devices this scaling calculation is done internally after the current transformer primary, secondary and

machine nominal currents are known.

Figure. 5.2.1. - 3. Nominal current calculation in differential protection relay

Normally the primary current ratings for phase current transformers are from 10A to thousands of

Amps and their decimal multiples, while normal secondary current ratings are 1 and 5A. Other, non-

standard ratings can be directly connected too since the scaling settings are flexible in large ranges.

For ring core current transformers the ratings may be different. Ring core current transformers are

commonly used for sensitive earth fault protection and their rated secondary may be as low as 0.2 A in

some cases.

In following chapter is given example for the scaling of the relay measurements to the example current

transformers and nominal load.

CT scaling example (application 1)

The connection of CTs to the IED measurement inputs and the ratings of the current transformers and

transformer nominal current are as in following gure.

AQ-T256

Instruction manual

Version: 2.00

Figure. 5.2.1. - 4. Example connection (S1 always to odd connector regardless the CT direction). CT direction is selected under

differential function

Please see the above gure, as a result of the direction of the CTs and according to the fact that P1/S1

side of the CTs are always wired to the odd inputs of the relay CT module, the “Differential calculation

mode” under the

Protection

→

TrafoModule

→

Idx> [87T,87N]

→

Settings

has to be set as “Subtract”.

Due to this the direction of measured currents are checked correctly from the relay perspective.

Initial data of the connection and the ratings are presented in following table.

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Instruction manual

Version: 2.00

13 © Arcteq Relays Ltd

Table. 5.2.1. - 4. Initial data from example connection.

High voltage side CT:

CT primary 800A

CT secondary 1A

HV-side nominal current:

669A

Ring core CT in Input I02:

3I0CT primary 250A

3I0CT secondary 1A

Low voltage side CT:

CT primary 8000A

CT secondary 1A

LV-side nominal current:

5888A

Both CTs are pointing through the transformer (HV-S2 and LV-S2 are pointing to same direction).

Nominal current for both high voltage and low voltage side of the protected transformer are calculated

based on given values under the “Transformer Characteristics” menu, which is located under the

protection main menu. CT module 1 and 2 ratio can be set directly under the same menu, or optionally

under

Measurement

→

Transformers

–menu. Per unit (PU) scaling is automatically set as xed to

“Object In p.u.” in all machine protection relays and it cannot be changed.

Figure. 5.2.1. - 5. Phase current transformer scaling to machine nominal.

As it can be seen in the gure above, the high voltage side nominal current is calculated to be 669.2A

and the low voltage side current is 5888.97A. These nominal currents are calculated as follow:

Per unit values for high –and low voltage side nominal currents can be calculated as shown below:

AQ-T256

Instruction manual

Version: 2.00

To multiply the per unit value with Phase CT secondary side current, it is possible to get the nominal

secondary current of transformer as Amperes. This current can be used when the unit is

commissioned and the directions of CTs are checked. See an example calculation below:

In case coarse residual current (I01) input is used for CT sum (Holmgren) input then it should be set to

phase current CT ratings 100/5A.

Figure. 5.2.1. - 6. Residual current I01 scaling to summing connection.

For the sensitive residual current (I02) measurement the CT primary and secondary currents are set

directly as rated currents 250/1A.

Figure. 5.2.1. - 7. Residual current I02 scaling to ring core CT input.

CT scaling example (application 2)

The connection of CTs to the IED measurement inputs and the ratings of the current transformers and

transformer nominal current are as in following gure.

AQ-T256

Instruction manual

Version: 2.00

15 © Arcteq Relays Ltd

Figure. 5.2.1. - 8. Example connection (S1 always to odd connector regardless the CT direction). CT direction is selected under

differential function

Please see the above gure, as a result of the direction of the CTs and according to the fact that P1/S1

side of the CTs are always wired to the odd inputs of the relay CT module, the “Differential calculation

mode” under the

Protection

→

TrafoModule

→

Idx> [87T,87N]

→

Settings

has to be set as “Add”. The

difference to the rst application is that here the CTs are pointing towards the protected object instead

of pointing through it.

Initial data of the connection and the ratings are presented in following table.

Table. 5.2.1. - 5. Initial data from example connection.

Machine nominal power: 153MVA

Machine high voltage side nominal amplitude: 132kV

Machine low voltage side nominal amplitude: 15kV

AQ-T256

Instruction manual

Version: 2.00

High voltage side CT:

CT primary 800A

CT secondary 2A

HV-side nominal current:

669A

Ring core CT in Input I02:

3I0CT primary 250A

3I0CT secondary 1A

Low voltage side CT:

CT primary 8000A

CT secondary 5A

LV-side nominal current:

5888A

Both CTs are pointing through the transformer (HV-S2 and LV-S2 are pointing to same direction).

The nominal currents on high voltage and low voltage side are exactly the same as in application 1.

The only difference is that the secondary current level of the CTs have been changed to 2A on high

voltage side and to 5A on low voltage side. Nominal currents are still calculated the same way:

Per unit values for high –and low voltage side nominal currents can be calculated as shown below:

To multiply the per unit value with Phase CT secondary side current, it is possible to get the nominal

secondary current of transformer as Amperes. This current can be used when the unit is

commissioned and the directions of CTs are checked. In application 2 it is necessary to inject higher

amplitudes to the CTs via secondary injection tool to reach the nominal currents. See an example

calculation below:

Settings

Table. 5.2.1. - 6. Settings of the Phase CT scaling

Name Range Step Default Description

Scale

meas to In

0:CT

nom

p.u.

1:Object

In p.u.

-

0:CT

nom

p.u.

Selection of the IED per unit system scaling reference, either the set phase

current CT primary or protected object nominal current. (NOT APPLICABLE IN

MACHINE PROTECTION).

Phase CT

primary

1…

5000.0A

0.1A 100.0A Rated primary current of the CT in amperes.

Phase CT

secondary

0.2…

10.0A

0.1A 5.0A Rated secondary current of the CT in amperes.

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Instruction manual

Version: 2.00

17 © Arcteq Relays Ltd

Nominal

current In

1…

5000A

0.01A 100.00A

Protected object nominal current in amperes. (This setting is visible if “Scale meas

to In” setting is set to “Object In p.u.”)

IL1

Polarity

0:-

1:Invert

- 0:-

IL1 (rst current) measurement channel polarity (direction) selection. Default

setting is that positive current flow is from connector 1 to connector 2 and the

secondary currents starpoint is towards line.

IL2

Polarity

0:-

1:Invert

- 0:-

IL2 (second current) measurement channel polarity (direction) selection. Default

setting is that positive current flow is from connector 3 to connector 4 and the

secondary currents starpoint is towards line.

IL3

Polarity

0:-

1:Invert

- 0:-

IL3 (third current) measurement channel polarity (direction) selection. Default

setting is that positive current flow is from connector 5 to connector 6 and the

secondary currents starpoint is towards line.

CT

scaling

factor P/S

- - -

IED feedback value, this is the calculated scaling factor for primary /secondary

current ratio

CT

scaling

factor

NOM

- - -

IED feedback value, this is the calculated ratio in between of set primary and

nominal currents.

Ipu

scaling

primary

- - - IED feedback value, scaling factor from p.u. value to primary current.

Ipu

scaling

secondary

- - - IED feedback value, scaling factor from p.u. value to secondary current.

Table. 5.2.1. - 7. Settings of the residual I01 CT scaling

Name Range Step Default Description

I01 CT

primary

1…

5000.0A

0.1A 100.0A Rated primary current of the CT in amperes.

I01 CT

secondary

0.2…

10.0A

0.1A 5.0A Rated secondary current of the CT in amperes.

I01 Polarity

0:-

1:Invert

- 0:-

I01 (coarse residual) measurement channel polarity (direction) selection. Default

setting is that positive current flow is from connector 7 to connector 8.

CT scaling

factor P/S

- - -

IED feedback value, this is the calculated scaling factor for primary /secondary

current ratio

Table. 5.2.1. - 8. Settings of the residual I02 CT scaling

Name Range Step Default Description

I02 CT

primary

1…

5000.0A

0.1A 100.0A Rated primary current of the CT in amperes.

I02 CT

secondary

0.1…

10.0A

0.1A 5.0A Rated secondary current of the CT in amperes.

I02 Polarity

0:-

1:Invert

- 0:-

I02 (ne residual) measurement channel polarity (direction) selection. Default

setting is that positive current flow is from connector 9 to connector 10.

CT scaling

factor P/S

- - -

IED feedback value, this is the calculated scaling factor for primary /secondary

current ratio

Measurements

Following measurements are available from the measured current channels.

Table. 5.2.1. - 9. Per unit phase current measurements

Name Range Step Description

AQ-T256

Instruction manual

Version: 2.00

Phase current ILx

0.00…

1250.0xIn

0.01xIn

Per unit measurement from each phase current channel fundamental

frequency RMS current.

Phase current ILx

TRMS

0.00…

1250.0xIn

0.01xIn

Per unit measurement from each current channel TRMS current including

harmonics up to 31

st

.

Peak to peak

current ILx

0.00…

500.0xIn

0.01xIn

Per unit measurement peak to peak current from each phase current

measurement channel.

Table. 5.2.1. - 10. Primary phase current measurements

Name Range Step Description

Primary Phase

current ILx

0.00…

1000000.0A

0.01A

Primary measurement from each phase current channel fundamental

frequency RMS current.

Phase current ILx

TRMS pri

0.00…

1000000.0A

0.01A

Primary measurement from each current channel TRMS current including

harmonics up to 31

st

.

Table. 5.2.1. - 11. Secondary phase current measurements

Name Range Step Description

Secondary Phase

current ILx

0.00…

300.0A

0.01A

Secondary measurement from each phase current channel fundamental

frequency RMS current.

Phase current ILx

TRMS sec

0.00…

300.0A

0.01A

Secondary measurement from each current channel TRMS current including

harmonics up to 31

st

.

Table. 5.2.1. - 12. Phase current angles measurements

Name Range Step Description

Phase angle ILx 0.00…360.00deg 0.01deg Phase angle measurement of the three phase current inputs.

Table. 5.2.1. - 13. Per unit residual current measurements

Name Range Step Description

Residual current

I01

0.00…

1250.0xIn

0.01xIn

Per unit measurement from residual current channel I01 fundamental

frequency RMS current.

Residual current

I02

0.00…

1250.0xIn

0.01xIn

Per unit measurement from residual current channel I02 fundamental

frequency RMS current.

Calculated I0

0.00…

1250.0xIn

0.01xIn

Per unit measurement from calculated I0 current fundamental frequency RMS

current.

Phase current I01

TRMS

0.00…

1250.0xIn

0.01xIn

Per unit measurement from I01 residual current channel TRMS current

including harmonics up to 31

st

.

Phase current I02

TRMS

0.00…

1250.0xIn

0.01xIn

Per unit measurement from I02 residual current channel TRMS current

including harmonics up to 31

st

.

Peak to peak

current I01

0.00…

500.0xIn

0.01xIn

Per unit measurement peak to peak current from I01 residual current

measurement channel.

Peak to peak

current I02

0.00…

500.0xIn

0.01xIn

Per unit measurement peak to peak current from I02 residual current

measurement channel.

Table. 5.2.1. - 14. Primary residual current measurements

Name Range Step Description

Primary residual

current I01

0.00…

1000000.0A

0.01A

Primary measurement from residual current channel I01 fundamental

frequency RMS current.

Primary residual

current I02

0.00…

1000000.0A

0.01A

Primary measurement from residual current channel I02 fundamental

frequency RMS current.

AQ-T256

Instruction manual

Version: 2.00

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