AC System: When using KEJIA® KDY series power surge protectors for three-phase four-wire power systems, four units can be connected in parallel between the protected terminals and ground (L, N lines and PE), which is called the TN-S connection method. Alternatively, three units can be connected in parallel between L and N lines, with an additional gas discharge surge protector connected between N and PE lines, known as the TT connection method. For single-phase power systems, one surge protector can be connected in parallel between each of the L and N lines to ground (PE).

DC System: When using KEJIA® KDY series DC power surge protectors, two surge protectors can be connected in parallel between the two lines of the DC power system and ground (+, - lines and PE), and the PE terminal grounding must be reliable.

RS-485 Communication Series (optional): The power surge protector is a combination product of power surge protection and NKP-LJ-04 surge detection communication. This product features a high-brightness LED digital display that can collect the failure status of the surge protection module, lightning strike counts, and lightning strike occurrence times, and send signals to the background management system through the RS485 interface. For the button operations and communication methods of the NKP-LJ-04 communication module, please refer to its user manual.

Precautions for Surge Protective Device (SPD) Installation

1、For the KDY-I-25RX power surge protective device (SPD), the power protection modules should be connected in parallel between the protected terminals and ground (L1, L2, L3, N lines and PE). The device adopts DIN35 rail mounting and can be installed in power distribution boxes or standard cabinets. For the communication module: the working power terminals must connect to the protected side of the SPD; the sampling current transformer should be connected in series with the SPD's down conductor; the remote signal terminals should connect to the SPD's alarm contacts to indicate failure status; the RS-485 serial port should connect to remote intelligent management units or SCADA systems.

2、During installation, the SPD's PE terminal must be securely connected to the nearest grounding point to provide an unobstructed discharge path.

3、Device address: Hexadecimal 01H-FFH (Decimal 1-255). Default is 01 at startup, configurable via buttons to match the connected SPD's number.

4、Baud rate: Selectable 9600, 4800, 2400, 1200, or 600 bit/s. Default is 9600 bit/s at startup, configurable via buttons.

5、Equipped with RS-485 communication interface using simplified MODBUS-RTU protocol for communication with management systems.

6、Maximum strike count: 99 events (resets to 01 after reaching maximum).

7、Data retention: Maintains data during power outages with storage capability up to 10 years without power.

NKP-LJ-04 Communication Module Terminal Definitions

1 —— Power L/+
2 —— Power N/-
3 —— RS-485 Communication A
4 —— RS-485 Communication B
5 —— SPD Remote Signal (YX) Contact 1 (non-polarized)
6 —— SPD Remote Signal (YX) Contact 2 (non-polarized)
7 —— CT Output 1 (non-polarized)
8 —— CT Output 2 (non-polarized)

Product Dimensional Drawing