What Is a Meter Relay?
A meter relay is a device combining a meter gauge with a contact output function. Commonly used in power and control systems, it not only displays values like a regular meter gauge but also detects abnormalities and responds promptly to system issues.
Applications of Meter Relays
Meter relays have diverse industrial applications:
1. Power System Control
Used in power circuits, meter relays prevent overloads by detecting overcurrent and disconnecting the circuit. They also manage voltage fluctuations and integrate renewable energy sources, monitoring energy generation and supply for stable power system operation.
2. Equipment Control
These relays monitor and control machinery such as pumps and fans. By setting upper and lower current limits, meter relays can detect and respond to equipment malfunctions, such as air trapping in pumps, and trigger alarms.
Principle of Meter Relay
Meter relays consist of a sensing section, a pointer/spring mechanism, and a relay section. They detect current and voltage through built-in sensors. When the sensed value overlaps with the setpoint on the relay, an internal spring mechanism triggers a contact action, generating an output. Some models use a contactless transistor output.
Types of Meter Relays
Meter relays vary based on the input signal:
1. Current Relay
Current relays detect current using a built-in current transformer (CT), which converts high current to a lower, detectable level. They are used for electric motor protection and overcurrent protection in power distribution lines.
2. Voltage Relay
Voltage relays use built-in voltage sensors (Potential Transformers or PTs) to detect and convert high voltage to a lower, manageable level. These relays are vital for voltage protection and control in power systems.
3. Temperature Relay
Temperature relays use sensors like thermistors or thermocouples to detect and respond to temperature changes, protecting equipment and systems from overheating and maintaining temperature within a specific range.