Trip Circuit Supervision Relay Wiring Diagram
Trip circuit supervision relay is a critical safety relay used in switchgear systems that monitors the integrity of circuit breaker trip circuits. We rely heavily on circuit breaker tripping for protecting entire switchgear system. If any fault arises, Protection relay should sense it and trip the breaker. But what happens if circuit breaker fails to operate during such faulty conditions. The role of trip circuit supervision relays is to constantly monitor the healthiness of the circuit breaker trip circuit. This comprehensive guide explains trip circuit supervision relay wiring diagrams using the ABB TCS relay as a practical example, helping you understand installation, operation, and troubleshooting. In this article we will discuss about connection diagram and its working principle through example of ABB make TCS relay.
What is a Trip Circuit Supervision Relay?
A trip circuit supervision relay (TCS) is a protective device designed to keep a vigilant eye on the health and integrity of circuit breaker trip circuits. It ensures that the trip coil circuit remains functional at all times, providing early detection of faults such as:
- Loss of auxiliary voltage supply
- Circuit breakage or open connections in the path of tripping coil.
- Neutral path not available for trip coil.
- Trip coil failures
The TCS relay is particularly critical for circuit breakers with a single trip coil where protection reliability is paramount, such as in generator circuit breakers, transmission line protection, and critical distribution networks.
ABB TCS Relay Connection Diagram
Before moving into connection diagram, it is necessary to understand the objective and how to achieve them. So the inventors of TCS relay had used a simple idea of passing a small (milli-Ams) current through the trip coil continuously irrespective of the state of the breaker (open or close). in simple terms if any milli-ampere current circulates through Trip coil, then this means that (a) all connections are proper (b) Trip coil in not burnt or open state (c) neutral is connected. So in a fault condition when relay operates and closes the auxiliary supply switch, the power supply will reach to trip coil and operate it as all connections are through.
If any of the connections is not proper or coil is burnt, the milli-amps circulating current will not flow. In such cases the TCS relay will give indication and if configured with hooter it will give alarm also.
Now lets understand the circuit diagram of ABB’s TCS relay. ABB’s TCS relay supervises the trip coil circuit using four main terminals (1–4), powered by an auxiliary supply (Uaux), and monitored via output alarm contacts (5–14).
Main Terminals:
- 1–4: Connected to the trip circuit of the breaker
- a–b: Auxiliary supply input to this Relay.
- 5–14: Output alarm contacts (for annunciator or alarm or SCADA input)
The relay provides continuous supervision for both the breaker open and breaker closed positions.
Operating Principle of ABB TCS Relay
The relay injects a small DC current (~2–3 mA) through the trip coil to verify continuity. This current is too low to energize the trip coil but sufficient to confirm that the trip path is healthy.
1️⃣ Supervision in Pre-Close Condition
(Refer to Fig. 2)
When the breaker is open, a current of ~2 mA flows through the trip coil supervision path.
This ensures that the trip coil and wiring are healthy before breaker closing.
If the circuit is open, the relay signals a Trip Circuit Fault Alarm.
2️⃣ Supervision in Post-Close Condition
(Refer to Fig. 3)
After the breaker is closed, a ~3 mA current continues flowing in reverse direction.
This allows supervision to continue during the load-carrying state, ensuring the circuit is ready for the next tripping command.
3️⃣ Supervision with Latched Trip Relay
(Refer to Fig. 4)
If the breaker trips and the trip relay latches, the supervision circuit still remains active.
This ensures the fault can be identified and acknowledged before resetting the breaker.
Key Features and Functions
| Feature | Function |
|---|---|
| Dual Condition Supervision | Monitors both open and closed breaker conditions. |
| Alarm Indication | Triggers an alarm on trip circuit failure. |
| Fail-Safe Operation | Continues monitoring after a trip event. |
| Compact Case Design | Suitable for standard 1/2S case panel mounting. |
| High Reliability | Maintains system protection readiness. |
Relay Connection & Dimensions
Connection Overview:
- Trip coil connected between terminals 3–4.
- Supervision path linked via terminals 1–2.
- Auxiliary supply connected to terminals a–b.
- Output alarm contacts (5–14) used for remote monitoring.
Typical Dimensions (in mm):
- Height: 158 mm
- Width: 102 mm
- Depth: 103 mm
Typical ABB TCS Relay Specifications
| Parameter | Specification |
|---|---|
| Supervision current | ~2–3 mA |
| Operating voltage | 24V / 30V / 48V / 110V / 220V DC |
| Relay contacts | Up to 4 changeover |
| Mounting | Flush / Panel |
| Indication | LED or Mechanical Flag |
| Function | Trip circuit health monitoring |
Why TCS Relay is Essential in Protection Systems
The Trip Circuit Supervision relay is the silent guardian of your protection system.
It ensures that your breaker will trip when required by:
- Detecting circuit discontinuities before faults occur.
- Monitoring control wiring, contacts, and fuses 24×7.
- Providing visual and remote alarm for maintenance teams.
Practical Example
In a 132 kV substation, if the breaker trip coil fuse blows unknowingly, the protection relay may fail to operate during a fault.
However, the ABB TCS relay instantly detects this issue and sends an alarm, allowing maintenance staff to restore the circuit before any trip failure occurs.
Conclusion
The ABB TCS Relay provides dependable supervision for circuit breaker trip circuits, ensuring safe, reliable, and uninterrupted protection system operation.
By continuously monitoring both pre-close and post-close conditions, it guarantees that your circuit breaker’s trip function will always be ready when needed.
In short: A TCS relay ensures your protection system never fails silently.
FAQs on TCS Relay
Q1. What does TCS relay stand for?
TCS stands for Trip Circuit Supervision — a relay used to monitor the continuity of a circuit breaker’s trip coil.
Q2. Why is trip circuit supervision important?
It ensures that faults like open wires, blown fuses, or contact failures are detected early, guaranteeing the breaker will trip when commanded.
Q3. What is the supervision current in ABB TCS relay?
The supervision current typically ranges between 2–3 mA DC.
Q4. Can TCS relay detect post-trip failures?
Yes. The relay continues monitoring even after tripping, ensuring the circuit is ready for the next operation.
Conclusion
Trip circuit supervision relays are essential components in modern power protection systems. The ABB TCS relay, with its low-level current injection principle and robust design, provides reliable continuous monitoring of circuit breaker trip circuits. Understanding the wiring diagrams for different circuit breaker conditions ensures proper installation and operation.
Implementing trip circuit supervision significantly improves system reliability by detecting faults before they can compromise protection systems. Whether in generator protection, transmission lines, or industrial applications, the TCS relay serves as a critical safeguard against protection system failures./heading
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References
- ABB – Trip Circuit Supervision Relay Type TCS Technical Datasheet
- Electrical4u.com– TCS Relay
- Trip Circuit Supervision Relay– electricaltopic.com
