Earth leakage relay is a protection device that detects the difference between the phase and neutral currents in the circuit (i.e., residual current) to determine ground faults, electric shocks, or insulation damage.
When the residual current is detected to exceed the set action value (such as 30mA, 100mA, 300mA, and other common rated action currents) and lasts longer than the action time (such as 30ms, 100ms, 300ms, etc.), the protector will automatically cut off the power supply to prevent electric shocks and electrical fires.
Earth leakage relay types by leakage current waveform
Residual current protection is divided into Type A, Type F, Type B and other types according to the detectable leakage current waveform type. The functions are gradually enhanced and suitable for different application scenarios.
Type A can monitor AC leakage and pulsating DC leakage, and is mainly used in residential, commercial and general industrial electrical systems to protect against conventional grounding faults and electric shock risks.
Based on Type A, Type F increases the detection capability of high- and low-frequency composite waveform leakage current and improves anti-interference performance. It is suitable for occasions with complex waveform interference such as frequency converters, inverters, welding machines, elevators, airport lighting, etc. to ensure the safe operation of the system.
Type B is the highest level at present, which can monitor AC, pulsating DC, composite and smooth DC residual currents below 1000Hz, and is suitable for systems with higher requirements for leakage protection and more complex leakage waveforms, such as variable speed drives, photovoltaic inverters, wind power generation, electric vehicle charging piles, UPS, medical equipment, machine tools, rail transit and welding machines.
Earth leakage relay types by power supply type
AC Earth Leakage Relay: An earth leakage relay powered by an AC auxiliary supply, typically AC 110V / 230V / 400V. It continuously monitors the leakage current in an AC power system through a connected current transformer (CT), and trips when the leakage exceeds the preset threshold.
Typical Applications:
- Industrial AC distribution systems
- Building electrical panels
- Motor control centers (MCC)
- Generators, transformers, and AC equipment
DC Earth Leakage Relay: An earth leakage relay powered by a DC auxiliary supply, typically DC 12V / 24V / 48V / 110V. It monitors leakage current in a DC power system or DC side of equipment and triggers protective action if leakage current exceeds the threshold.
Typical Applications:
- DC power distribution systems
- Battery energy storage systems (BESS)
- Photovoltaic (PV) systems DC circuits
- Electric vehicle (EV) charging stations (especially Mode 3 & Mode 4 DC charging)
- UPS systems and telecommunications power systems
Earth leakage relay types by internal signal processing technology
Digital Earth Leakage Relay
A digital earth leakage relay utilizes microprocessor-based signal processing technology to analyze the leakage current signal captured by an external current transformer (CT). The relay converts the analog signal into a digital value through an A/D converter and processes it via embedded algorithms for precise measurement, adjustable trip thresholds, and programmable delay settings.
Digital relays typically offer features such as multi-range trip current settings (30mA to 30A), adjustable time delay (30ms to 500ms), display screen with real-time leakage current values, Modbus RS485 communication, remote reset, and event history storage.
Analog Earth Leakage Relay
An analog earth leakage relay processes the leakage current signal directly through analog circuits, typically using operational amplifiers, comparators, and timing circuits. When the detected leakage current exceeds a preset threshold set by a potentiometer or DIP switch, the analog circuitry triggers trip output. Analog relays are known for their fast response, simple structure, and low cost, with typical trip current settings ranging from 30mA to 10A, and fixed or limited adjustable delay times such as 30ms, 100ms, or 300ms.
Earth leakage relay types by brands
Delab Earth Leakage Relay
Delab is a local industrial electrical brand in Malaysia, focusing on economical and standard residual current protection solutions. The products cover Type A and Type B, with adjustable leakage action current and delay function, suitable for distribution cabinets, generators, motor control cabinets and other occasions. Simple operation, good anti-interference ability, suitable for Southeast Asia and general industrial distribution environment.
Schneider Earth Leakage Relay
Schneider Electric is a leading global industrial electrical brand, providing high-reliability digital Earth Leakage Relay, covering Type A/F/B and DC leakage detection capabilities. With Modbus communication, LCD real-time display, event recording and remote reset functions. The products are widely used in photovoltaics, UPS, electric vehicle charging stations and high-end industrial plants to meet the needs of complex waveform detection.
ABB Earth Leakage Relay
ABB has a complete residual current protection product line, focusing on digital multi-function leakage relays, supporting Type A/F/B/DC leakage waveform detection. It has programmable action current, delay, RS485 communication and multi-stage pre-alarm functions. It is suitable for large industrial plants, data centers, new energy charging piles and heavy-load distribution systems, with stable and reliable performance.
Siemens Earth Leakage Relay
Siemens provides high-end digital Earth Leakage Relay, mainly Type A/F/B products, and some models support DC leakage monitoring. It has Modbus communication, event recording, LCD display and remote reset functions, and excellent anti-interference design. It is widely used in Industry 4.0 intelligent power distribution systems, rail transit, data centers and industrial automation production lines.
Prok DVS Earth Leakage Relay
Prok DVS is an Indian industrial electrical brand, focusing on mid-range economical Earth Leakage Relay solutions. The products cover Type A and Type B, providing analog and digital types, supporting adjustable leakage current and action delay. It is suitable for conventional industrial power distribution, computer rooms, and building electrical control systems, with high cost-effectiveness.
GIC Earth Leakage Relay
GIC is committed to providing compact and economical earth leakage protection relays suitable for OEM and light industrial occasions. Products cover Type A and Type B, and some models support multi-stage action delay settings. Small size, easy installation, suitable for small and medium-sized distribution boxes, mechanical equipment, general industrial electric control cabinets, and stable reliability.
Selec Earth Leakage Relay
Selec is a well-known industrial electric control brand in India, providing a wide range of Earth Leakage Relay models, mainly Type A and Type B, and a small number of high-end models support Type F. It has multiple stages of leakage action current and delay settings, and some models have Modbus communication. It is suitable for distribution boxes, motor control, office buildings, and factory power distribution systems, with high cost performance.
Broyce Control Earth Leakage Relay
British Broyce Control focuses on high-performance industrial residual current protection, and its products cover Type A/F/B types, and some models have anti-interference filtering and high-frequency detection functions. Supports RS485 communication, alarm preset, multi-stage leakage current and delay setting, suitable for complex scenarios such as medical, data center, new energy power generation, charging station, etc., with extremely high reliability.
Hobut Earth Leakage Relay
Hobut is a long-established British industrial electrical brand, providing analog Earth Leakage Relay and CT combination solutions. The products are mainly Type A and Type B, with fast response speed and simple structure. Suitable for conventional power distribution applications such as generators, low-voltage distribution cabinets, industrial control systems, etc., with moderate price and good stability.
Eaton Earth Leakage Relay
NHP Earth Leakage Relay
NHP, a well-known Australian electrical brand, provides Earth Leakage Relay that is compatible with Australian power distribution standards, and mainly supports Type B/F/DC leakage waveform detection. It has anti-interference design, Modbus communication and early warning functions, and is suitable for mining areas, UPS, data centers and EV charging piles, especially for high-frequency DC and complex waveform scenarios.
Conclusion
Earth leakage relays are essential components in protecting electrical systems and personnel from insulation faults. Choosing the right type involves considering factors such as leakage current waveform, power system type, signal processing technology, and product availability. As electrical systems become more complex, Type B and digital earth leakage relays are increasingly preferred for their advanced detection and monitoring capabilities, while AC and analog models remain reliable choices for conventional applications. Careful relay selection ensures both operational safety and system performance.
