What is earth leakage protection
Earth leakage protection is a highly sensitive protection measure
Earth Leakage CT for ELR-4MA AC Earth Leakage Relay
Blue Jay’s ELR-4MA AC Earth Leakage Relay is a high-performance protection device designed to monitor residual currents and enhance electrical safety in industrial and commercial systems. Using a residual current transformer (ie, earth leakage CT) (RCT), it detects leakage currents and triggers alarms when thresholds are exceeded, preventing electrical hazards.
earth leakage CT - Type AC, A, F and B Residual Current Transformers
RCTs detect leakage currents in electrical systems, each type suited for different applications:
earth leakage CT - Type AC RCT
Function: monitors the residual sinusoidal AC current that is suddenly applied or slowly rising. Suitable for linear loads, sensitive only to sinusoidal AC.
Applicable scenarios: Single-phase AC loads without rectifiers in industrial and commercial buildings.
Typical equipment: Electric heaters, industrial ovens, high-power vacuum cleaners, resistive load equipment.
earth leakage CT - Type A RCT
Function: Monitors the pulsating DC residual current and the pulsating DC residual current superimposed with 6mA smooth residual current, which contains the characteristics of the AC type. Applicable to equipment with rectifier loads, it can detect sinusoidal AC and pulsating DC components.
Applicable scenarios: Equipment containing electronic rectifier components in commercial buildings and office spaces.
Typical equipment: Electromagnetic heating equipment, industrial microwave ovens, smart dishwashers, computers and office equipment in office buildings.
earth leakage CT - Type F RCT
Function: In addition to the faults covered by Types A and AC, Type F RCT covers the residual current with multiple frequencies up to 1000Hz. However, the residual fault current should limit the pure dc component to 10mA or lesser. Their representation includes a sine wave, a pulsating dc, and a high-frequency sine wave.
Applications scenarios: designed for single-phase variable frequency loads, which involve AC/DC conversion and high-frequency switching components.
Typical equipment: Industrial HVAC systems, frequency-controlled water pumps, heat pumps, and other single-phase variable frequency-driven equipment.
earth leakage CT - Type B RCT
Function: Contains the protection characteristics of Type A, and in addition, it can monitor the sinusoidal AC residual current of 1000Hz and below, AC residual current superimposed with smooth DC residual current, pulsating DC residual current superimposed with smooth residual current, pulsating DC residual current generated by two-phase or multi-phase rectifier circuits, and smooth DC residual current.
Applicable scenarios: industrial automation, transportation and new energy applications, equipment involving variable frequency drive and AC/DC conversion.
Typical equipment: cranes, cranes, elevators, industrial frequency conversion equipment, three-phase photovoltaic inverters, electric vehicle charging piles, medical and mining isolated power supply monitoring systems.
How to Select the Earth Leakage CT for Earth Leakage Relays?
Most earth leakage relays can monitor earth leakage current from 10 mA to 300 mA (max 500 mA). Because the earth leakage relay must be used with earth leakage current transformers, you need to choose a suitable earth leakage CT. How to select?
Step 1: You must understand the magnitude of the leakage current in the circuit. Only then can you determine the appropriate specifications for the leakage current transformer.
Step 2: Ensure that the current transformer ratio of the selected earth leakage current transformer matches the current transformer ratio of the earth leakage relay. For example, if your earth leakage CT has a ratio of 2000:1, then your earth leakage relay should also have a current transformer ratio of 2000:1. The common earth leakage CT ratios are 600:1, 1000:1, and 2000:1. Blue Jay can provide all these types of earth leakage current transformers. Here are the details specification in the following:
Model
Sepcification
Size
F-1025
0-100A
Rectangular copper busbar 100*25mm
F-1435
0-250A
Rectangular copper busbar 140*35mm
F-1835
0-400A
Rectangular copper busbar 180*35mm
F-2245
0-630A
Rectangular copper busbar 220*45mm
F-2645
0-800A
Rectangular copper busbar 260*45mm
F-3045
0-1250A
Rectangular copper busbar 300*45mm
F-4545
0-2500A
Rectangular copper busbar 450*45mm
CTZ6-025
0-63A
Circular Cable entry φ25mm
CTZ6-045
0-100A
Circular Cable entry φ45mm
CTZ6-065
0-250A
Circular Cable entry φ65mm
CTZ6-080
0-400A
Circular Cable entry φ80mm
CTZ6-100
0-630A
Circular Cable entry φ100mm
CTZ6-150
0-800A
Circular Cable entry φ150mm
CTZ6-200
0-1600A
Circular Cable entry φ200mm
Conclusion
The ELR-4MA currently supports AC and A-type detection, ensuring precise leakage monitoring for industrial and commercial environments. This enhances safety, minimizes downtime, and protects equipment. For B and F-type applications, Blue Jay Technology continues to innovate to meet evolving industry needs.
By understanding the differences between AC, A, B, and F-type RCTs, users can select the appropriate protection device, ensuring reliability and compliance in modern electrical systems.
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Earth leakage Vs Residual and Zero-sequence Current – What’s the Difference
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Blue Jay’s ELR-4MA AC Earth Leakage Relay is a high-performance protection device designed to monitor residual currents and enhance electrical safety in industrial and commercial systems. Using a residual current transformer (ie, earth leakage CT) (RCT), it detects leakage currents and triggers alarms when thresholds are exceeded, preventing electrical hazards.
earth leakage CT - Type AC, A, F and B Residual Current Transformers
RCTs detect leakage currents in electrical systems, each type suited for different applications:
earth leakage CT - Type AC RCT
Function: monitors the residual sinusoidal AC current that is suddenly applied or slowly rising. Suitable for linear loads, sensitive only to sinusoidal AC.
Applicable scenarios: Single-phase AC loads without rectifiers in industrial and commercial buildings.
Typical equipment: Electric heaters, industrial ovens, high-power vacuum cleaners, resistive load equipment.
earth leakage CT - Type A RCT
Function: Monitors the pulsating DC residual current and the pulsating DC residual current superimposed with 6mA smooth residual current, which contains the characteristics of the AC type. Applicable to equipment with rectifier loads, it can detect sinusoidal AC and pulsating DC components.
Applicable scenarios: Equipment containing electronic rectifier components in commercial buildings and office spaces.
Typical equipment: Electromagnetic heating equipment, industrial microwave ovens, smart dishwashers, computers and office equipment in office buildings.
earth leakage CT - Type F RCT
Function: In addition to the faults covered by Types A and AC, Type F RCT covers the residual current with multiple frequencies up to 1000Hz. However, the residual fault current should limit the pure dc component to 10mA or lesser. Their representation includes a sine wave, a pulsating dc, and a high-frequency sine wave.
Applications scenarios: designed for single-phase variable frequency loads, which involve AC/DC conversion and high-frequency switching components.
Typical equipment: Industrial HVAC systems, frequency-controlled water pumps, heat pumps, and other single-phase variable frequency-driven equipment.
earth leakage CT - Type B RCT
Function: Contains the protection characteristics of Type A, and in addition, it can monitor the sinusoidal AC residual current of 1000Hz and below, AC residual current superimposed with smooth DC residual current, pulsating DC residual current superimposed with smooth residual current, pulsating DC residual current generated by two-phase or multi-phase rectifier circuits, and smooth DC residual current.
Applicable scenarios: industrial automation, transportation and new energy applications, equipment involving variable frequency drive and AC/DC conversion.
Typical equipment: cranes, cranes, elevators, industrial frequency conversion equipment, three-phase photovoltaic inverters, electric vehicle charging piles, medical and mining isolated power supply monitoring systems.
How to Select the Earth Leakage CT for Earth Leakage Relays?
Most earth leakage relays can monitor earth leakage current from 10 mA to 300 mA (max 500 mA). Because the earth leakage relay must be used with earth leakage current transformers, you need to choose a suitable earth leakage CT. How to select?
Step 1: You must understand the magnitude of the leakage current in the circuit. Only then can you determine the appropriate specifications for the leakage current transformer.
Step 2: Ensure that the current transformer ratio of the selected earth leakage current transformer matches the current transformer ratio of the earth leakage relay. For example, if your earth leakage CT has a ratio of 2000:1, then your earth leakage relay should also have a current transformer ratio of 2000:1. The common earth leakage CT ratios are 600:1, 1000:1, and 2000:1. Blue Jay can provide all these types of earth leakage current transformers. Here are the details specification in the following:
| Model | Sepcification | Size |
| F-1025 | 0-100A | Rectangular copper busbar 100*25mm |
| F-1435 | 0-250A | Rectangular copper busbar 140*35mm |
| F-1835 | 0-400A | Rectangular copper busbar 180*35mm |
| F-2245 | 0-630A | Rectangular copper busbar 220*45mm |
| F-2645 | 0-800A | Rectangular copper busbar 260*45mm |
| F-3045 | 0-1250A | Rectangular copper busbar 300*45mm |
| F-4545 | 0-2500A | Rectangular copper busbar 450*45mm |
| CTZ6-025 | 0-63A | Circular Cable entry φ25mm |
| CTZ6-045 | 0-100A | Circular Cable entry φ45mm |
| CTZ6-065 | 0-250A | Circular Cable entry φ65mm |
| CTZ6-080 | 0-400A | Circular Cable entry φ80mm |
| CTZ6-100 | 0-630A | Circular Cable entry φ100mm |
| CTZ6-150 | 0-800A | Circular Cable entry φ150mm |
| CTZ6-200 | 0-1600A | Circular Cable entry φ200mm |
Conclusion
The ELR-4MA currently supports AC and A-type detection, ensuring precise leakage monitoring for industrial and commercial environments. This enhances safety, minimizes downtime, and protects equipment. For B and F-type applications, Blue Jay Technology continues to innovate to meet evolving industry needs.
By understanding the differences between AC, A, B, and F-type RCTs, users can select the appropriate protection device, ensuring reliability and compliance in modern electrical systems.
Related articles
Type B Earth Leakage Relay – A Comprehensive Guide
Type B earth leakage relay is a Type B
Earth leakage Vs Residual and Zero-sequence Current – What’s the Difference
Although earth leakage, residual current, and zero-sequence current are
