How to check the fault of street lamp line

First, quickly check the short-circuit fault point of street lamp line.

In the operation of street lamps, the poles, lamp holders and other parts are prone to short circuit. The street lamp line is long, and there are many inspection wells and street lamps, which are scattered, so it is difficult to detect the fault point. When a short circuit is found, the fault range (in the sucker rod, in the well and in the protective tube) should be detected first, and then it should be dealt with as soon as possible. The most commonly used method in practice is DC resistance method, which needs to cut off the cable, which is labor-intensive and slow. In fact, the method of capacitor current limiting is simpler and easier, and the speed can be greatly improved without damaging the cable. The following briefly introduces two methods.

1, DC resistance detection method for short circuit fault.

Street lamp line is a typical uniformly distributed load. Street lamps divide the line into sections of 30-40 meters. In the three-phase four-wire system, generally, the primary circuit does not exceed 20 street lamps, numbered 1#, 2#, 3#, 18 #, 19# and 20#, and each phase has an average of 7 street lamps, such as phase A: 1#, 4#. The principle of "half distance" can be adopted. First, cut off the phase A of the cable in 10# pole or well, and measure the DC resistance, and make sure that the fault range is within half of the street lamp line, and the detection range is (1). If the fault is found to be between 1 ~ 10 # street lamp, the principle of 50/50 can be adopted to cut off the A phase of the cable in the 5# pole or well, and the fault range cannot be determined at the end of measuring DC resistance (2). If the fault is found between 1 ~ 5 # street lamps, the principle of 50/50 can be adopted to cut off phase A of 3# pole or cable in the well, and measure DC resistance to ensure that the fault range is within the detection range (3). If a fault is found between 1 ~ 3 # street lamps, the principle of 50/50 can be adopted to cut off the A phase of 2# pole or cable in the well, measure the DC resistance and determine the fault range. So far, it can be determined that the short circuit fault is in the pole, well or protective tube. The short circuit between the rod and the well can be reconnected or entangled to eliminate the fault. If the short circuit occurs in the protection tube, the cable should be replaced.

"Half-distance" principle: use a multimeter to monitor the cable, first monitor the cable at 1/2 (the midpoint), then monitor the abnormal section at 1/2, then monitor the remaining abnormal section at 1/2, and so on, gradually narrow the scope, and finally determine the cable fault range.

2. Capacitance current limiting method

After determining the direction of the faulty cable, the two short-circuited cable cores are removed from the distribution circuit to separate them from all other cable cores. The short-circuit fault cable core is connected in series with the 30vf capacitor in the distribution cabinet, and indirectly connected with the 220V power supply through the capacitor. At this time, the contact resistance of the short-circuit point will become smaller, about a few ohms, which can be ignored and not calculated. Therefore, after the capacitor current is limited, the AC current of about 2 A appears stably in the cable. Starting from the power supply point, use the clamp ammeter to measure the current in the rod or well point by point in the direction of the fault point according to the principle of "three rods and one measurement". If there is current, the fault point is far from the power supply, and continue to measure downward. When the measured current is getting smaller and smaller until there is no current, the fault point is between the two monitoring points, which can be measured point by point, gradually narrowing the range, and the position of the short circuit point can be determined soon.

Advantages and disadvantages:

When the cable is short-circuited, DC resistance detection method needs to cut off the cable to measure and judge the direction of the fault point. After finding the fault point, the cut cables should be reconnected and made one by one. It increases the consumption of manpower and material resources, prolongs the troubleshooting time, and greatly reduces the efficiency of emergency repair. Moreover, sometimes the length of the cable in the pole is insufficient, and the effective length after truncation can not meet the requirements of making the cable intermediate head, which causes great difficulties.

The capacitor is small in size, light in weight and convenient to connect and disassemble. Capacitance current limiting method is to make a stable and obvious current value appear in the cable by using capacitance. You can measure the current value without cutting the cable, just use the clamp ammeter. In street lamp maintenance, capacitor is also a standing material, which can be found at any time on site. This method is very suitable for the investigation of street lamp lines, and there is no need to cut the cable, and of course there is no need to connect and make cable heads, which can greatly reduce the consumption of manpower and material resources and greatly improve the speed of emergency repair. The effective length of that cable is not reduce, and the service life of the cable is prolonged.

Safety precautions: The first method has no safety threat to human body because it is not charged. Capacitance current limiting method, the cable is charged, so we should always pay attention to potential safety hazards.

The second is to quickly check the fault point of street lamp line open circuit.

1, the phase line is broken. You can quickly determine the range of cable disconnection by observing how the light goes out.

2. The zero line is broken. The three-phase power supply line shows that the phase voltage at the end of the line is obviously unbalanced and the neutral point deviates seriously. The voltage of individual phases is too high, which causes the bulb to burn out. When the neutral line of single-phase power supply line is disconnected, the light below will not light up, so it is easy to find the fault point.