Transmission Line Differential Protection
ED7-L

The ED7-L series IEDs provide one integrated platform for the protection, control and monitoring of transmission lines 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 protection is designed as individual sets, installed at different ends of protected double- or triple-ended line and connected by digital channels.

Apart from differential protection, IED also supports distance and back-up current line protections.

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 96 binary inputs and output relays in total. Binary inputs have no common contact

IED has up to 16 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-L protection function	ANSI code	For lines with three pole operated CB

Line differential protection	87L
Distance protection	21
Power swing blocking	68
Remote tripping	85
Earth-fault protection	50N/51N/67N
Overcurrent protection	50/51
Directional overcurrent protection	67
Inrush detector	INR
Automatic switch onto fault logic	SOTF
Undervoltage protection	27
Residual overvoltage protection	59N
Overvoltage protection	59
Negative sequence overvoltage protection	47
Phase Discontinuity Protection	46BC
Built-in communication interface for protections

Tripping logic	94
Trip circuit supervision	74TC	O
Breaker failure protection	50BF
Synchrocheck, energizing check and synchronizing	25	O
Autorecloser (3 Phase)	79	O
Autorecloser (1 Phase)	79SP
Lockout	86	O
Fuse Failure / VT Supervision	60
Circuit breaker control / Supervision	52	O
CT Supervision
Open-phase protection		O

Three-phase Measurement
One-phase Measurement
Fault locator	21FL

Disturbance recorder
Event recorder
Self-test function

— basic functions

O — optional functions

Application

Used as protection on double-end, three-end (including with three-way supply) and dead-end overhead transmission lines

Bias value selection capability

using module of current phasor difference (relation between the bias value and the current phase shift at the ends of the line). The bias value shall be maximum in case of external fault and minimum in case of internal faults (short-circuit)
using the sum of current phasor modules (the bias value is independent of the phase angle between currents at the ends of the line and shall be the same in case of inner and outer short circuits)
using a special “sectoral” blocking characteristic (block zone shall be determined using the module of ratio of the current phasors at the ends of the line and the mutual angle between them)

The bias is used to offset the imbalances caused by non-similarity of current measuring transformers and their operating conditions

Redundancy of communication channels

The device can use two independent fully redundant digital channels

Command exchange between devices

16 additional commands can be used to exchange signals between any external devices, for example, to remotely control circuit-breakers or exchange IED internal logical signals common for two protection devices

Line backup protection

In order to back up the line differential protection in case of digital channel loss, the device includes: five-zone distance protection against phase-to-phase faults and one-zone protection against single-phase ground faults, five-stage directional earth-fault protection and instantaneous overcurrent protection

Communication between devices

via a dedicated optical channel using optical cable cores (multimode or single-mode fiber). Maximum optical cable length: 200 km
using multiplexer equipment for communication channel multiplexing (via electrical (X21 or G703.1) or optical (IEEE C37.94) interface)

Capacitive current compensation

Protection logic compensates capacitive currents of cable lines (over 20 km long) and overhead lines (over 150 km long) to offset the additional line differential protection imbalance that occurs in case of external fault

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). Devices remain operable within 150 ms after power loss

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	up to 150

Maximum continuous air temperature, °C	+55
Minimum continuous air temperature, °C	-5
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, А	5
Switching capacity of contacts (making current)	up to 30 А for 0.20 s
Maximum operation time, ms	10

Transmission Line Differential ProtectionED7-L

Display

Electronic switches

Two-color LEDs

Functional control

USB port

Binary inputs and output relays

Analog inputs

Line Differential Protection Communication / Communication ports

Functions

Features

Specifications

Transmission Line Differential Protection
ED7-L