Energy storage power supply manufacturer analysis in the photovoltaic system, the electrical switch has two main roles: First, the electrical isolation function, in the installation and maintenance, cut off the electrical connection between the photovoltaic modules, inverters, distribution cabinets and power grid, to provide a safe environment for the operator, this action is the initiative of the operator to achieve; second is the safety protection function, when the electrical system occurs in the overcurrent, overvoltage, short circuit over temperature and leakage The second is the safety protection function, when the electrical system overcurrent, overvoltage, short-circuit overtemperature and leakage, can automatically cut off the circuit to protect the safety of personal and equipment, this action is automatically achieved by the switch.
Therefore, when the photovoltaic system if the switch tripped, one of the reasons is that the switch may over-current, over-voltage, over-temperature, leakage current, the following analysis of the solution to the causes of each situation.
1 Current reasons
This failure is the most common, the circuit breaker selection is too small or the quality is not up to par. When designing, first calculate the maximum current of the circuit, the rated current of the switch should exceed 1.1 times to 1.2 times the maximum current of the circuit. Judgment basis: Usually it does not trip, but only when the weather is very good and the power of the PV system is high. Solution: Replace the circuit breaker with a high rated current or a reliable quality circuit breaker.
Small circuit breakers have two types of C and D, which is the type of release, the difference between C and D type is the difference in short-circuit instantaneous release current, overload protection is the same. C type magnetic release current is (5-10) In, that is, when the current 10 times the rated current trip, the action time is less than or equal to 0.1 seconds, suitable for the protection of conventional loads. D type magnetic release current is (10-20) In, that is When the current is 20 times the rated current, the action time is less than or equal to 0.1 seconds, which is suitable for protecting equipment with high inrush current. When the switch before and after the transformer and other electrical equipment, there is an inrush current after the power failure, you should choose D-type circuit breakers, if the line does not have transformers and other inductive equipment, it is recommended to choose C-type circuit breakers.
2 Voltage reasons
This fault is relatively rare, between the two phases of the circuit breaker, there is a rated voltage, generally single extremely 250V, if more than this voltage may trip. There may be two reasons: one is the wrong choice of the rated voltage type of the circuit breaker; the second is that when the power of the PV system is greater than the load power, the inverter to increase the voltage to send power out. Judgment basis: use a multimeter to measure the break voltage, more than the rated voltage of the circuit breaker. Solution: Replace the circuit breaker with a higher rated voltage, or a cable with a larger wire diameter to reduce the line impedance.
3 temperature causes
This failure is also more common, the circuit breaker labeled rated current, is the device at a temperature of 30 degrees can pass the maximum long-term current, the temperature increases by 10 degrees per 5% reduction in current. The circuit breaker is also a source of heat because of the presence of contacts. There are two reasons for the high temperature of the circuit breaker: First, the circuit breaker and cable contact is poor, or the circuit breaker itself contact is not good, internal resistance, resulting in the breaker temperature rise; Second, the circuit breaker is installed in a place where the environment is closed to poor heat dissipation.
Judgment basis: circuit breaker action, touch with your hand, feel the temperature is high, or see the terminals have a high temperature, or even the smell of burning.
Solution: re-wire, or replace the circuit breaker.
4 leakage causes
Line or other electrical failure, other electrical equipment leakage, line leakage, component or DC line insulation layer damage.
Judgment basis: between the positive and negative components and AC phase line, low insulation resistance between the positive and negative components, phase line and ground line.
Solution: Detect and replace the faulty equipment and wires.
When the trip caused by leakage fault, the cause must be identified to remove the fault before re-closing the circuit breaker, forcible closing is strictly prohibited. Leakage circuit breaker occurs when the breakage tripped, the handle is in the middle position, when re-closing, you need to first toggle the operating handle down (break position), so that the operating mechanism to re-buckle together, and then up to close.
How to choose the leakage protector for PV system: As PV modules are installed outdoors, the DC voltage is high when multiplexed in series, and there will be a small amount of leakage current from the module to the ground, so when choosing a leakage switch, the leakage current protection value should be adjusted according to the size of the system. Generally, a conventional 30mA leakage switch is only suitable for installation in single-phase 5kW or three-phase 10kW or less systems, beyond this capacity, the leakage current protection value should be increased appropriately.
Photovoltaic systems with isolation transformers can reduce the occurrence of leakage current, but if the isolation transformer is wired incorrectly or has leakage problems itself, it may also trip due to leakage current.
Summary
If the PV system has a switch tripping event, if it is a longer installed power station, one of the reasons may be the wiring problem of the circuit or the aging problem of the switch. If it is a newly installed power station, it is possible that the switch is improperly selected, the line insulation is poor, the transformer insulation is poor, and other problems.
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