Description

GRLE8-S Digital Earth Leakage Relay

The GRLE8-S is a digital earth leakage relay designed for monitoring and measuring residual current in single-phase and three-phase power systems. Working with an external zero-sequence current transformer (ZCT), it performs Type A true RMS measurement across a 30mA to 30A setting range and provides two-stage protection through a separate pre-alarm relay and trip relay. A wide AC85-265V supply input, adjustable 0-99.9s trip delay and a 36mm DIN rail housing make it a practical fit for distribution panels, motor control centers and machine protection circuits.

Working Principle

Under normal conditions, the vector sum of load currents passing through the ZCT equals zero. When insulation deteriorates or a leakage path to earth forms, an imbalance appears and the ZCT feeds a proportional signal to the relay via terminals S1-S2. The GRLE8-S calculates the true RMS value of this residual current and compares it against two thresholds: when leakage exceeds the alarm level, the alarm relay R2 (terminals 21-24) operates as an early warning; if leakage continues to rise past the trip set value IΔn and the programmed delay Δt elapses, the trip relay R1 (terminals 11-14) operates to open the circuit breaker. Each output has its own release hysteresis: adjustable from 5 to 40% for the trip relay, and fixed at 10% of the alarm set value for the alarm relay, preventing contact chatter near either threshold.

Informative LCD Display

Dual readout — measured residual current IΔ and set value IΔn shown simultaneously.
Trend bar — 25% / 50% / 75% segments light up as leakage approaches the set value, revealing insulation deterioration before any relay operates.
Status icons — trip output, alarm, delay-running, R1/R2 contact action, RUN and SET states each have a dedicated indicator.
Units shown — %, mA and s displayed directly for clear reading.

Key Features

Type A true RMS measurement — detects sinusoidal AC and pulsating DC residual currents accurately.
Two-stage protection — independent alarm relay for pre-warning and trip relay for disconnection.
Instant trip at 30mA — when IΔn is set to 0.03A, Δt is forced to 0 for personnel protection.
Selectable relay logic — normal mode Nd or Ne (fail-safe energized mode) and reset mode ON/OFF to suit the control scheme.
ZCT self-diagnosis — an open or shorted transformer circuit triggers a flashing “Ct Err” indication on the display.
Remote test and reset — short T-C terminals to simulate a fault, R-C terminals to reset; also available from the front T/R button.
Fast response — ≤30ms when trip current exceeds 5× set value; ≤50ms at 1× set value.
Power-on delay — 0.5 to 99.9s adjustable, avoiding nuisance trips from inrush transients at startup.

Protection & Reliability

Trip accuracy is held within ±5% of the set current and ±5% of set time ±50ms. Trip relay hysteresis is configurable from 5 to 40% of the trip level, while the alarm relay uses a fixed 10% hysteresis for stable pre-warning behavior. The unit operates from -20°C to +55°C, carries IP20 protection, overvoltage category III and pollution degree 2 ratings, and offers a mechanical life of 1×10⁷ operations with an electrical life of 1×10⁵ operations at AC1 load.

Installation & Wiring

The relay mounts on standard 35mm DIN rail per EN/IEC 60715 in any position. Supply connects to A1-A2 (AC85-265V, 50/60Hz, 3VA burden) and the ZCT to S1-S2 using shielded or twisted-pair cable of at least 1m; remote test/reset wiring to the T-C and R-C terminals should not exceed 10m. All live conductors including neutral pass through the ZCT, while the PE conductor stays outside. The trip output pairs with an MCCB fitted with either an undervoltage release (MN) or a shunt trip coil (MX). Terminals accept 1×2.5mm² or 2×1.5mm² conductors at 0.4N·m. Compact 90×36×70mm housing (95mm high including the DIN rail clip), 118g. A matching ZCT (ZCT26AL to ZCT200AL, aperture Ø26-Ø200mm) is ordered separately according to cable size.

Applications

Suitable for earth leakage monitoring and protection in industrial distribution boards, commercial building installations, pump and motor circuits, HVAC systems and machine tools — anywhere insulation condition in single-phase or three-phase networks needs continuous supervision to IEC 60947-2.

Technical Parameters

Item	GRLE8-S
Function	Earth leakage relay
Supply terminals	A1-A2
Voltage range	AC85-265V, 50/60Hz
Burden	3VA
Operation range	30mA to 30A
Trip level limits	85% of set value
Trip time delay	0 to 99.9s (forced to 0 when IΔn = 0.03A)
Power-on time delay	0.5 to 99.9s
Reset time	~2s
Response time	≤30ms (trip current > 5× set value); ≤50ms (trip current = 1× set value)
Hysteresis (trip relay R1)	5 to 40% of trip level, adjustable
Hysteresis (alarm relay R2)	10% of set alarm leakage current, fixed
ZCT detection	Absent or short (“Ct Err” indication)
Accuracy	Trip: ±5% of set trip current; Time: ±5% of set time ±50ms
Reset mode	Manual / Auto reset
Output	2×SPDT: trip relay R1 (11-12-14), alarm relay R2 (21-22-24)
Current rating	10A / AC1
Switching voltage	250VAC / 24VDC
Min. breaking capacity DC	500mW
Mechanical life	1×10⁷
Electrical life (AC1)	1×10⁵
Operating temperature	-20°C to +55°C
Storage temperature	-35°C to +75°C
Humidity	Up to 95% RH (non-condensing)
Mounting / DIN rail	DIN rail EN/IEC 60715
Protection degree	IP20
Operating position	Any
Overvoltage category	III
Pollution degree	2
Max. cable size (mm²)	1×2.5mm² or 2×1.5mm², 0.4N·m
Dimensions	90mm×36mm×70mm (95mm high incl. DIN rail clip)
Weight	118g
Standards	IEC 60947-2

Frequently Asked Questions

1. What is the GRLE8-S earth leakage relay?

A digital, DIN rail mounted relay that monitors and measures residual (leakage) current in single-phase and three-phase power systems through an external zero-sequence current transformer (ZCT). It displays live values on an LCD and trips its output relays when leakage exceeds the set threshold.

2. What are its core functions?

Measurement — Type A true RMS residual current detection, 30mA to 30A.
Trend indication — 25%/50%/75% display segments show how close leakage is to the set value.
Pre-alarm — alarm relay R2 (terminals 21-24) warns before trip level is reached; fixed 10% hysteresis.
Tripping — trip relay R1 (terminals 11-14) with 0-99.9s delay and adjustable 5-40% hysteresis; forced instant trip at the 0.03A setting.
Diagnosis — an open or shorted ZCT circuit triggers a “Ct Err” display warning.
Control — front T/R button or remote T-C/R-C terminals; manual or automatic reset.

3. Which parameters matter most when selecting this relay?

Trip current IΔn — choose within 30mA-30A per protection level (e.g. 30mA for personnel, 300mA for fire protection).
Supply voltage — AC85-265V, 50/60Hz on terminals A1-A2.
Time delay — 0-99.9s trip delay for selectivity with downstream devices.
Output rating — 10A/AC1 at 250VAC/24VDC must match the breaker coil or alarm circuit.

4. What models and voltage options are available?

The series follows the code GRLE8-S/□, where “S” indicates the digital display type and the suffix defines the rated control supply voltage. The standard option is A265: AC85V-265V. A matching zero-sequence current transformer is required and selected separately by cable diameter.

5. Which standards does it comply with, and where is it used?

The relay is designed to IEC 60947-2 and mounts on DIN rail per EN/IEC 60715, with overvoltage category III and pollution degree 2 ratings. These IEC-based specifications suit markets across Europe, the Middle East, Southeast Asia, Africa and South America where 50/60Hz IEC installations are standard.

6. What should I note during installation and maintenance?

Wiring — pass all live conductors (not PE) through the ZCT; connect supply to A1-A2.
Torque — tighten terminals to 0.4N·m; cable size 1×2.5mm² or 2×1.5mm².
Environment — operate at -20°C to +55°C, ≤95% RH non-condensing; IP20 requires enclosure mounting.
Routine check — use the T/R button periodically to verify the trip function.

GRLE8-S Earth Leakage Relay with Digital Display