The correct wiring of the residual current protection device is related to whether the protection device can operate correctly, and also relates to the normal operation of the protection device, and whether it can protect against personal electric shock, electrical equipment damage, and electrical fire accidents.
First, the residual current protection device wiring points
1, according to the low-voltage system grounding type to determine the wiring method
Before installing the wiring, the residual current protection device should first check the grounding type of the low-voltage system. The grounding type of the low-voltage system in China has TT, TN and IT systems. Since the IT system forms a closed system and is used under special circumstances and has high safety performance, the residual current protection device is generally not used as the personal electric shock and electrical fire protection, and will not be discussed here.
In the TN system, it can be divided into TN-C, TN-CS, and TN-S systems. The wiring requirements of the residual current protection device in the TT, TN-CS, and TN-S systems are different. In the TN-C system, the residual current protection device cannot be installed. It must be modified to TN-CS, TN-S or local TT. The system can be installed. In the TN-CS system, the requirements for installing the residual current protection device are more stringent, otherwise the wiring error may cause malfunction or rejection.
1 Wiring requirements in the TT system
In the TT system, whether it is a 220 V power supply electrical equipment, it is connected to a two-pole two-wire residual current protection device, or a three-phase four-wire 380 V power supply electrical equipment shared by a three-phase device and a single-phase device. With a three-pole four-wire or four-pole four-wire residual current protection device, the neutral line must pass through the residual current protection device.
2 Wiring requirements in the TN-S system
In the TN-S system, the wiring requirements of the above 1.1.1 in the TT system must be met, and the protection (PE) line must not pass the residual current protection device.
3 Wiring requirements in the TN-CS system
The TN-CS system was modified from the TN-C system. Only the TN-C system can be transformed into a TN-CS system, a TN-S system or a partial TT system. It is only allowed to install the residual current protection device.
The TN-CS system wiring must meet the requirements for N-line and PE lines in 1.1.1 and 1.1.2 above.
In the TN-CS system, the residual current protection device is only allowed to use a separate portion between the N line and the PE line. The N line through the residual current protection device shall not be used as a PE wire, and shall not be grounded repeatedly.
The N line on the load side of the residual current protection device can only be used as a neutral line and must not be shared with other circuits.
The distribution line of the TN-C system is required to operate. When the N line must be repeatedly grounded, the residual current protection device should not be used as the line power terminal protection.
2. Determine the wiring method according to the power supply of the electrical equipment.
For single-phase 220 V power supply electrical equipment, a phase line and an N line should be connected through the two-pole two-wire residual current protection device.
For three-phase three-wire 380 V power supply electrical equipment, three phase conductors should be connected through the three-pole three-wire residual current protection device.
Three-phase four-wire 380 V power supply electrical equipment, when three-phase equipment and single-phase equipment share the circuit wiring, there should be three phase lines and one N line through the three-pole four-wire or four-pole four-wire Residual current protection device.
The three-pole four-wire or four-pole four-wire residual current protection device is divided into two types: the neutral pole can not be disconnected and can be disconnected. The wiring should be matched with the power supply mode.
The wiring methods described above are all shown in Table 1.
Second, other matters needing attention
1. The load side and power side must be separated when wiring
When the electronic residual current protection device is connected, the load side and the power supply side must be separated, because the trip unit of the electronic residual current protection device only turns on the thyristor after the residual current transformer has a fault signal output, and instantaneously turns on the voltage. The coil trips the circuit breaker , and the voltage coil should be powered off immediately after the power is turned off. If the load side and the power supply side are reversed, after the residual current breaker is activated, there is still a voltage applied to the voltage coil, and there is a possibility that the voltage coil is burned out.
2. Wiring must be correct
Since the three-pole three-wire, three-pole four-wire or four-pole four-wire residual current protection device can be used in a single-phase circuit, the test resistance does not have to be changed, but the wiring must be correct. The phase line and neutral (N) line of the single-phase power supply must be connected to the corresponding terminal of the test resistor. Otherwise, it will not work when the test button is tested for action.
In the wiring of the residual current protection device, many specific problems are encountered. Especially in the TN-CS system, the TN-C system is modified, and the wiring error is often caused by the confusion of the N line and the PE line. Therefore, it is necessary to determine the correct wiring method according to the specific situation. Under normal circumstances, it can be wired according to the wiring method of the residual current protection device in GB13955-2005, as shown in the figure in Table 1.
Note 1: L1, L2, L3 are phase lines; N is neutral; PE is protection line; PEN is neutral and protection line; single or three-phase electrical equipment; single-phase lighting equipment; Residual current protection device; for the grounding of a separate grounding device that is not connected to the neutral grounding point of the system.
Note 2: In the wiring diagram of single-phase load or three-phase load in different ground protection systems, the left device is not equipped with residual current protection device, and the middle and right sides are wiring diagrams for installing residual current protection device.
Note 3: In the electrical equipment using the residual current protection device in the TN-C system, the protective line exposed to the conductor should be connected to a separate grounding device to form a local tt system, such as the right in the TN-C system wiring diagram. Side equipment with * wiring.
Note 4: The TN-S and TN-CS grounding types in the table, the middle and right wiring diagrams in the wiring diagrams of single-phase and three-phase loads are grounding methods according to the site conditions.
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