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S5700 Series Switches Hardware Description

This document provides an overall description of the S5700 hardware, helping you obtain detailed information about each chassis, card, power module, fan module, cable, and optical module.
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WLA220W01-20 kA Surge Protector

WLA220W01-20 kA Surge Protector


A 20 kA surge protector (model: WLA220W01) protects the 220 V single-phase power system and powered devices against the surge voltage caused by lightning strikes.


A 20 kA surge protector uses an integrated base to facilitate installation and maintenance, and provides an alarm port (dry contact point) for remote monitoring.

Figure 11-3 shows the appearance of a 20 kA surge protector.

Figure 11-3 Appearance of a 20 kA surge protector


A 20 kA surge protector uses the 3+1 protection circuit and provides overheat and overcurrent protection. When the surge protector fails, it is automatically disconnected from the power grid to avoid fire caused by a short circuit.

When the status indication window of a surge protector is red, the surge protector fails and must be replaced immediately. If a remote alarm buzzer is connected to the surge protector, the alarm buzzer will generate alarm signals.

Figure 11-4 shows the protection principles of a 20 kA surge protector.

Figure 11-4 Protection principles of a 20 kA surge protector

Application Scenario

When the S5720I-SI series switches are installed in outdoor cabinets, 20 kA surge protectors must be used in some scenarios. Ensure that the following requirements are met:
  • AC switch:
    • If the 220 V mains supply is used, install a 20 kA surge protector between the power port of the switch and the mains.
    • If power is supplied by an isolated inverter near the outdoor cabinet, no surge protector needs to be installed between the power port of the switch and the inverter.
  • DC switch: An isolated power supply must be used and placed in the same outdoor cabinet as the switch. Surge protection is required for the power input of the outdoor cabinet. The surge protector, power supply, and switch must be equipotential. The outdoor cabinet must be properly grounded and the grounding impedance must be less than or equal to 10 ohms. If a DC switch is connected to the PAC-260WA-E or PAC240S56-CN power module that is powered by the 220 V mains, install a 20 kA surge protector between the power input port of the PAC-260WA-E or PAC240S56-CN and the mains.

The 20 kA surge protector and S5720I-SI switch can be decoupled using 5-10 m power cables or decoupling inductors, as shown in Figure 11-5 and Figure 11-6.

Figure 11-5 Using 5-10 m power cables for decoupling

Figure 11-6 Using decoupling inductors for decoupling

  • The recommended cross-sectional area of a live wire/neutral wire (L/N) power cable for decoupling is 1.25 mm2.
  • The cross-sectional area of a PE ground cable must be greater than or equal to 16 mm2.
  • If there is no space for placing 5-10 m power cables in the cabinet for decoupling, install a hollow-core surge protection decoupling inductor with an inductance of 5-10 μH on both the L and N wires. The decoupling inductors need to be purchased separately.


Table 11-7 lists the specifications of a 20 kA surge protector.

Table 11-7 Specifications of a 20 kA surge protector



Dimensions (H x W x D)

72 mm x 90 mm x 65 mm (2.83 in. x 3.54 in. x 2.56 in.)

Nominal voltage

220 V AC

Maximum continuous operating voltage (Uc)

385 V AC

Maximum discharge current (Imax)

40 kA (8/20 μs)

Nominal discharge current (In)

20 kA (8/20 μs)

Protection level (Up)

1.8 kV

Status indication window (four red/green bi-color windows)

  • Green: normal state
  • Red: failure

Part number


Updated: 2019-08-19

Document ID: EDOC1000013597

Views: 561184

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