Transformer Protection
ED7-T

The ED7-T series IEDs provide one integrated platform for the protection, control and monitoring of transformer assets up to 765 kV with the latest in communication technologies. The IEDs are based on long-term field experience and focusing on the challenges our customers face.

The device implements the functions of the main and backup protection of the transformer.

It includes transformer differential protection, earth-fault protecion of HV side, overcurrent protection, overload protection, automatic cooling start relay, circuit breaker failure protection. It provides reception of signals from tripping stage of transformer gas protection, OLTC.

Front panel

Large graphic display is designed to show the information necessary for the user

16 electronic switches are used to enable/disable relay protection functions directly from the device front panel. Each electronic switch is fitted with LED indicator. They can be assigned to any program switch in IED logic circuit

The user assigns available versions:

32 LEDs with electronic switches,
48 LEDs w/o electronic switches.

These LEDs light up, when certain protections actuate. They can be freely configured for any internal logic signal

The following buttons are provided on the IED front panel:

alarm reset
local/remote control
circuit-breaker control functional buttons
selecting group of settings
keyboard

USB port for PC connection for setting up and configuring IED parameters

Rear view

Up to 160 binary inputs and output relays in total. Binary inputs have no common contact

IED has up to 32 analog inputs in various configurations

IEDs have several communication interfaces (RS-485, FOL, Ethernet (electrical/fiber-optic), 1PPS) and can be integrated into automation system of any enterprise

ED7-T protection function	ANSI code

Transformer differential protection	87T
Restricted earth fault protection (optional function)	87N
Overcurrent protection	50/51
Directional overcurrent protection (optional function)	67
Inrush detector	INR
Automatic switch onto fault logic	SOTF
Undervoltage protection	27
Residual overvoltage protection	59N
Overvoltage protection	59
Phase Discontinuity Protection	46BC

Tripping logic	94
Fuse Failure/ VT Supervision (optional function)	60
CT Supervision

Three-phase Measurement
One-phase Measurement

Disturbance recorder
Event recorder
Self-test function

Application

It is possible to select the type of protected equipment, as well as a certain set of differential protections

Up to 6 differential zones

It is possible to use the device as a single protection complex for a transformer, its busbars, reactors or line regulating transformer with a total number of independent differential zones up to 6. Including restriction earth fault protection (REF) can be implemented. All this eliminates the need for additional devices

Sensitive relay and instantanious overcurrent

The transformer biased differential protection contains a sensitive relay and a instantaneous overcurrent. The sensitive relay operates on differential current and actuates depending on the bias current. The tripping characteristic of the transformer differential protection sensitive relay consists of horizontal and slopes connected by a smooth transition

Differential protection instanteneous stage is designed to ensure reliable operation at high value fault currents in the protection zone

Second harmonic level monitoring

The second harmonic level in the differential current is monitored to adjust the transformer differential protection against magnetizing in-rush current

Earth fault protection

Earth fault protection on the HV side uses the rated current value 3I0 obtained by summing the phase currents

Combined voltage start

The device monitors the voltage circuits, which allows you to organize a combined voltage start and power direction relay for overcurrent protection

Self-test and test mode

Devices feature an advanced self-test system, ensuring continuous monitoring of hardware and software serviceability

Operation conditions

Devices operate at increased air humidity (≤ 80%), high positive and negative ambient temperatures (from -5 to +55 °C)

Data communication protocols

Supporting all modern protocols, communication standards (IEC 61850-8-1, IEC 61850-9-2LE, IEC 60870-5-103, Modbus RTU (with optional converter) and time synchronization protocols (SNTP, PPS (electrical and optical), PTPv2 (for SV))

Specification	Value

Rated alternating current, A	1 or 5 (selected via software)
Rated frequency, Hz	50
Rated AC voltage, V	100
Rated auxiliary DC voltage, V	110; 220

Operational voltage range	-20%…+10%
Interruption, ms	150

Maximum continuous air temperature, °C	+55°C
Minimum continuous air temperature, °C	-5°C
Upper humidity value, %	80
Ingress protection (IP) degree	IP40 - front panel IP20 - rear panel

Permissible overload of current inputs, continuous	2 * I_r
Permissible overload of current inputs, 1s	100 * I_r
Burden at I_r, VA	0.2
Permissible overload of voltage inputs, continuous	1.5 * U_r 1.8 * U_r for open delta
Burden at U_r, VA	0.2

Rated voltage	(1-300) VDC (1-400) VAC
Continuous current, A	5
Switching capacity of contacts (making current)	up to 30 А for 0.20 s
Maximum operation time, ms	10
Consumption per phase for AC voltage circuits at U_r, VA	0.2

Transformer ProtectionED7-T

Display

Electronic switches

Two-color LEDs

Functional control

USB port

Binary inputs and output relays

Analog inputs

Communication ports

Functions

Features

Specifications

Transformer Protection
ED7-T