1. Overcurrent Relay
An overcurrent relay, often abbreviated as CO, is a protective device that activates when the current flowing through it exceeds a pre-set threshold. It plays a crucial role in protecting electrical systems from damage caused by excessive currents, such as those resulting from short circuits or overloads. The most common type is the induction overcurrent relay, which operates using electromagnetic principles. This relay typically consists of an electromagnet and a rotating aluminum or copper disc. When the current exceeds the set value, the magnetic field induces rotation in the disc, triggering the relay to act.
The operating principle involves the use of a current transformer to step down the system current. This secondary current generates a magnetic field within the relay, causing the disc to rotate. However, this rotation only occurs when the current exceeds the relay's set point, ensuring protection against overloads without unnecessary tripping.
2. Overvoltage Relay
The overvoltage relay, commonly known as OV, is designed to protect electrical equipment from damage caused by voltage surges. When the system voltage rises above 120% of its rated value, the relay triggers the circuit breaker to disconnect the power supply. The structure of the inductive overvoltage relay is similar to that of an overcurrent relay, with the main difference being the configuration of the primary coil, which is optimized for detecting voltage rather than current.
3. Undervoltage Relay
The undervoltage relay, abbreviated as UV, functions similarly to the overvoltage relay but responds to low voltage conditions. It is used to protect equipment from damage due to insufficient voltage. Unlike the overvoltage relay, the internal contacts of the undervoltage relay are normally closed and will open when the voltage drops below a certain level, thereby disconnecting the circuit.
4. Ground Fault Overvoltage Relay
The ground fault overvoltage relay, also called OVG or grounding alarm relay (GR), is used in three-phase, three-wire ungrounded systems. It is connected to a grounded transformer in an open-delta configuration to detect zero-sequence voltage. This relay helps identify ground faults and provides early warning signals to prevent further damage to the system.
5. Ground Fault Overcurrent Relay
The ground fault overcurrent relay, abbreviated as GCR, is specifically used for high-voltage line grounding protection. Its main applications include:
6. Selective Grounding Relay
The selective grounding relay, often referred to as SG or directional grounding relay (DG), is used in non-grounded systems to identify and isolate faulty lines. It detects zero-sequence current using a grounding voltage transformer. When a ground fault occurs, the relay identifies the faulty line and sends an alarm signal. This allows for selective disconnection of the affected line while maintaining power to the rest of the system.
7. Phase Loss Relay
The phase loss relay, also known as OPR or phase loss protection relay (PHR), is used to detect and respond to single-phase operation in three-phase systems. If one of the phases is lost, the motor may run on only two phases, leading to overheating and potential damage. The relay quickly detects this condition and cuts off the power supply to prevent harm to the motor.
8. Ratio Differential Relay
The ratio differential relay, abbreviated as RDR, is used for differential protection in transformers, alternators, and AC motors. It differs from traditional overcurrent relays because it compares the current entering and leaving a protected element. In cases where external faults cause unbalanced currents or mismatched current transformer characteristics, the relay avoids false trips by analyzing the ratio of the currents. This ensures more accurate and reliable protection of critical electrical components.
A hydraulic gauge adaptor is a device used to connect a hydraulic gauge to a hydraulic system. It is typically a small, threaded component that acts as an interface between the gauge and the hydraulic system.
The adaptor is designed to fit into the hydraulic system's pressure port or test point, allowing the gauge to be securely attached. It ensures a tight seal to prevent any leakage or loss of pressure during testing or monitoring.
Hydraulic gauge adaptors come in various sizes and configurations to accommodate different types of hydraulic systems and gauges. They are often made of durable materials such as stainless steel or brass to withstand the high pressures and harsh conditions commonly found in hydraulic systems.
Overall, a hydraulic gauge adaptor is an essential tool for accurately measuring and monitoring hydraulic pressure in various applications, such as industrial machinery, automotive systems, and hydraulic equipment.
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