Factory Automation

Low-voltage Circuit BreakersEarth Leakage Relays

Earth Leakage Relays

Earth Leakage Relays

Unlike earth leakage circuit breakers, earth leakage relays do not interrupt, only detect a leakage current.
A ZCT (zero-phase current transformer) is used in combination with a relay. The ZCT detects a leakage current, and then the relay sends a signal.

Structure of an Earth Leakage Relay

ZCT (ZT30B)

Relay (NV-ZBA)

Examples of Possible Uses

  • Triggered by the leakage current detection, the leakage alarm can be output and only the relevant devices can be shut down while other devices continues to operate.
  • For use in large-capacity main circuits. (To the extent not covered by the earth leakage alarm breaker)
  • For use in motor control centers in combination with molded case circuit breakers with high breaking capacity.etc.
Types and uses Features and functions Circuit diagram
Compatibility Compact standard model
ZBA Series
(Electric self-holding type)
Ideal for motor control centers with limited space
  • Can be combined freely with a ZCT.
  • When a ground fault current is detected,
    it electrically self-holds and alerts the user to the incident.
  • Compact and 100/200V switchable.
  • Time-delay types can also be manufactured.
General-purpose model
ZSA Series
(Mechanical self-holding type)
General-purpose type that can be combined with an MCCB,
electromagnetic contactors,
etc. to create the desired circuit configuration
  • Can be combined freely with a ZCT.
  • When a ground fault current is detected,
    it electrically self-holds and alerts the user to the incident.
  • Can also be used for a 415V-circuit.
  • The output contacts control two circuits (1a1c).
  • Equipped with a mechanical earth leakage indicator.
  • Plug-in and time-delay types can also be manufactured.
Harmonic/surge-resistant type
ZHA Series
(Electric self-holding type)
Ideal for leakage current detection in inverter circuits
  • Can be combined freely with a ZCT.
  • When a ground fault current is detected,
    it electrically self-holds and alerts the user to the incident.
  • Accurate a leakage current can be detected by eliminating
    distortion of the inverter secondary side ground fault current.
  • The surge absorber prevents unwanted operation due to
    a transitional earth leakage current.
  • Simultaneously compliant with various international standards
    (U.S. UL standards, Canadian CSA standards,
    European CE marking, and U.K. UKCA marking).
Harmonic/surge-resistant type
ZLA Series
(Mechanical self-holding type)
Ideal for leakage current detection in inverter circuits
  • Can be combined freely with a ZCT.
  • When a ground fault current is detected, it electrically
    self-holds and alerts the user to the incident.
  • Accurate a leakage current can be detected by eliminating
    distortion of the inverter secondary side ground fault current.
  • The surge absorber prevents unwanted operation due to
    a transitional earth leakage current.
  • Simultaneously compliant with various international standards
    (U.S. UL standards, Canadian CSA standards,
    European CE marking, and U.K. UKCA marking).
  • Can also be used for the 480V-circuit.
For leakage alarms
ZAA Series
(Self-resetting type)
Ideal for leakage alarms
  • Can be combined freely with a ZCT.
  • Detects a ground fault current and notifies the user of
    an incident, but automatically resumes operation
    when the ground fault is eliminated by disconnecting
    the circuit at fault or by other measures.
    (Within 1.5 sec. of resetting time)
Earth leakage relay with a primary conductor
Ideal for large-capacity circuits
  • The primary conductor is built into the ZCT for a compact size and easy wiring.
  • The ZBA, ZSA, ZHA, ZLA, and ZAA series from 600A to 3200A can be manufactured.

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