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The selection and installation of SPD aren’t standardized, result in a large number of switches lightning strike

Publication Date:  2012-09-21 Views:  683 Downloads:  0

Issue Description

Versions Information: V100R005C01, S2700-9TP-SI-AC
Failure Phenomenon: When the S2709 port doesn’t plug the network cable, it can turn into UP by itself .11 faulty devices, 9 devices have one broken port. 2 devices have two broken ports.
Networking Overview:
1. Scene, Environment:
1) There are more than 100 sites in the scene,. Installation scene: dome camera +1 ~ 2 bolt camera + switch network box;
2) Network box internal installed  relatively standard;
3) Some sites network box inside switch because of network inside have ground point protective paint, lead to poor grounding situations.
4) XX city near has more thunderstorms in the near future, higher temperature; multiple devices have temperature alarm.
2. Networking Situation:
1) the network signal networking:
HD camera (dome camera ,box camera --- Haikang brand) - >2709 switch -> optical fiber transceivers –>Reese Dotcom SMVP device (Layer 1 Convergence) –> PTN device - mobile equipment room –> Police Network -> County Branch
2) Power Networking:
City Mains - >Power SPD (red) - >Power circuit breaker -> socket  1 -> power supply voltage stabilizer -> socket  2
Socket 1 power supply device type: lighting street lamps
Socket 2 - powered supply device type: 2709 Switch (220V); 24V AC adapter (a separate power cord is pulled away to supply dome camera); 12V DC adapter (four cables core supply for the box camera); optical fiber transceivers

Alarm Information

 Device has no abnormal alarm, but the switch appears service can not get through, device port doesn’t plug the network cable, it can turn into UP by itself, and lit the UP indicator. 

Handling Process

 Recommendation 1: Use Huawei certification 4 core network port SPD, replace the existing network SPD
Measure 1: Replace the existing network Ethernet port SPD.

Recommendation 2:  Use 8 core network port SPD or Huawei certification shipments SPD, replace the existing network SPD
Measures: Replace the existing network Ethernet port SPD.

Recommendation 3: Check the existing network equipment, to ensure that the switches and network port SPD are well grounded.
Measure 3: To ensure good grounding.

Root Cause

Existing network appears many such failures, trigger a common point, through the exploration of the environment of the scene, as well as laboratory simulation tests, found that there are some problems on the actual current network networking and selection configuration, these factors have led to the current network high failure rate, summarize as follows:
1. SPD selection error:
Hectomegametric  switch only use 4-wire to transmission, but lightning energy will also be sensitive to the eight cores line, you need to use 8-wire Ethernet port SPD in order to play the role of protective equipment, but the client site use 4-wire network port SPD.
2. SPD usage error:
SPD installation need to strictly obey the input and the output connection direction. The client builders reverse connect SPD, made SPD can’t achieve the protective effect, and even damage;
3. SPD design flaws:
SPD usually design decoupling circuit on the signal line to reduce the lightning energy that run into the rear protective device. But the client uses the four-wire SPD without the circuit design, there is a design flaw.
4. Existing network grounding problem:

Network boxes, switches, ground outlet, SPD ground line, required to be tandem on the same ground outlet, mine's ground rafts, and to be well grounded, in order to better discharge lightning energy.

The main reasons summarize:
Now ball camera group lightning adopt the 4-wire cable SPD use to protection 8 core scene, and the SPD has design defects, leading to common mode lightning energy is converted to differential mode energy, damage the switch port.


1. This SPD with design defect + incorrect installation, did not help to prevent lightning, and up to less than the switch itself 6KV prevent lightning effect.
2.  Front-line engineers rarely scene personally do hardware installation, especially the installation of low-end devices, so the piece of content about not many.  The installation piece SPD specification, a necessary condition for long-term stable operation of equipment is a very important.  The less hardware installation and implementation of the norms of the case, to seriously study the case, in order to correctly guide the installation.