1. Introduction

A protection relay for 220/400 V networks protects electrical circuits from faults such as over‑voltage, under‑voltage, over‑current and frequency deviations. It continuously monitors transitions and provides alarm/control outputs.

2. Safety Instructions

✔ Only qualified personnel may install and configure the device.
✔ Disconnect power before installation.
✔ Ensure correct voltage rating matches your network (400/220 V).
✔ Avoid exposure to moisture, dust and vibrations.

3. Installation

1. Mount the unit securely in a control panel or DIN rail.

2. Connect the power supply terminals according to polarity and rated voltage.

3. Connect input supply lines (L1, L2, L3, N) — for 3‑phase systems.

4. Connect protective earth (PE) ground.

5. Wire the output contacts (relay / alarm) to your control system.

6. If provided, connect communication interfaces (RS485/Ethernet).

4. Front Panel Controls

Common relay front panels include:
🟢 Status LEDs — Indicate power, alarm, communication and fault states.
🔘 Buttons / Display — Navigate settings, read measured values and fault logs.
📟 LCD Display — Shows real‑time voltage, frequency and protection status.

5. Operating Modes

Protection relays typically support:

Voltage Protection
✔ Over‑voltage trip
✔ Under‑voltage trip

Frequency Protection
✔ High frequency trip
✔ Low frequency trip

Time Delays
✔ Adjustable delay before trip to prevent nuisance faults.

6. Configuration

1. Access the menu via panel keys or a connected software tool.

2. Set nominal voltage (e.g., 220/400 V).

3. Adjust trip thresholds (e.g., upper/lower limits and time delays).

4. Save settings and return to monitoring mode.

7. Communication Setup

If the device has RS485 or Ethernet:

• Set the communication address and protocol (e.g., Modbus).

• Integrate with SCADA or BMS for remote monitoring.

8. Normal Operation

When powered ON:
✔ The relay continuously measures voltage and frequency.
✔ LEDs show system state (normal / fault).
✔ If a threshold is exceeded, the relay triggers and opens its contact to protect the system.

9. Alarm & Trip Conditions

Typical trip conditions:
⚠ Over‑voltage — load or line voltage too high
⚠ Under‑voltage — voltage drop below safe limit
⚠ Frequency deviation — generator or grid instability
After a trip, the display often shows the fault code.

10. Maintenance

✔ Periodically inspect terminals for corrosion and tightness.
✔ Update firmware if supported.
✔ Test the protection thresholds regularly for correct behavior.