Factors causing cable protector malfunction
During the use of cable protector, there will be some factors that cause it to malfunction. These factors are either internal or external. Everyone should understand and correct them after identifying the fault. The causes of cable protector malfunction are as follows:
1. Wiring failure
Misoperation can be caused by improper wiring of electrical equipment, interconnection of adjacent branch neutral wires, and improper selection of the number of missing poles. The most typical is the misoperation caused by the single-phase load neutral line directly connected to the power supply side of the protector.
2. Improper grounding
In the power distribution system, such as repeated grounding of the neutral wire, shunting from the grounding point of the lotus-coupling transformer, and poor grounding of the metal shielding layer in the zero-sequence current transformer loop, etc., this fault will occur.
3. Internal and external overvoltage
When lightning overvoltage occurs in the circuit or overvoltage during operation, due to the high frequency of overvoltage, the capacitive reactance to the ground is small, resulting in a large charging current, which often causes the cable protector to malfunction. In order to prevent this from happening, a resistor-capacitor overvoltage absorber is connected in parallel between the input and output contacts of the cable protector to suppress the occurrence of overvoltage.
4. Electromagnetic interference
When a magnetic device is connected or disconnected and a high-power device is opened and closed near the cable protector, the generated magnetic field will cause the cable protector to malfunction. In this case, the cable protector should be far away from the above equipment; if there is a high-power inverter in the line, a harmonic suppressor should be installed at the output of the inverter to prevent its malfunction.
5. Loop current
When two distribution transformers are operated in parallel, if the neutral point of each transformer has its own grounding wire, since the internal impedance of the two transformers cannot be exactly the same, circulating current will inevitably occur in the grounding wire. If the circulation is large, it will cause the cable protector to malfunction. In order to avoid such failures, one transformer grounding wire should be removed so that the two transformers share the same grounding electrode.
6. Reduced insulation of working zero line
If the insulation of the neutral wire in the power supply circuit is reduced, it will inevitably cause the detection circuit of the leakage protector to lose balance due to the current or voltage between the two wires of the fire and the neutral, which will cause the leakage protector to generate induced electromotive force, resulting in abnormal tripping due to malfunction. Therefore, the degree of insulation of the neutral line should also arouse the attention of our big guys.
7. The influence of overload or short circuit
When the cable protector has both over-current protection and short-circuit protection, improper current setting of the over-current short-circuit protection trip unit often causes the leakage protection switch to trip by mistake, for example, the short-circuit trip value is less than the rated working current value of the line. For this reason, the operating current of the overcurrent protection device should be re-adjusted to match the operating current.
Shandong Dibo Petroleum Machinery Co., Ltd
AddresS: Wei Zhuang Zhen, Xin County, Liaocheng City, Shandong Province