How many photovoltaics can each grid connected station access? What technical requirements should photovoltaic access meet?

According to relevant national standards, when the grid-connected capacity of photovoltaic and other distributed power sources exceeds 25% of the rated capacity of the distribution transformer, anti-island protection devices must be installed. The distributed anti-island protection device is actually a complete cabinet, mounted on the transformer side.

State Grid has a clear regulation for our problems. For the photovoltaic access, if no anti-island protection device is installed, the access system of the photovoltaic power station is only allowed to connect 25% of the photovoltaic. Depending on the local power supply department, photovoltaic capacity can reach 50 percent or 80 percent if anti-island devices are installed.

Anti-isolated island protection devices are mainly used in photovoltaic grid-connected systems. Their core role is to break the power supply balance by disturbed loads in equipment, so that external voltage detected by photovoltaic inverters is insufficient to meet normal power output and force inverters to stop, so as to achieve security maintenance. The distributed anti-islanding unit is actually a complete set of cabinets mounted on the transformer side. The anti-island is installed beside the transformer in the form of cabinet, which is used in conjunction with JP cabinet. The purpose is to deal with the isolated network in time when it is running. A disturbance through the resistance forces the inverter to stop working.

Distributed photovoltaic power generation anti-islanding device is designed to meet the automation needs of various small distributed photovoltaic power generation. On the basis of summarizing the development and research experience of power station automation system over the years, according to the needs of users, aiming at the impact of the islanding effect of distributed photovoltaic power generation connected to the distribution network on the on-site safety operation of power maintenance personnel, Designed for power users, with high cost-effective new protection equipment (220V/380V low-voltage anti-island device in the low-voltage distribution network). Based on the islanding operation mechanism and anti-islanding protection strategy of photovoltaic power generation, the anti-islanding function can be realized by destroying the conditions of islanding operation of distributed photovoltaic power generation.

So what are the main components of the anti-islanding device?

Shell: The anti-island protection device belongs to the outdoor installation of the control protection cabinet, the general material is 304 stainless steel, the protection grade is above IP44. Generally installed next to the JP cabinet of the transformer, and the installation distance from the JP cabinet can not be too far away, so that the installation and wiring is easier.

Disturbance resistance: disturbance resistance is a class of resistance, the selection of disturbance resistance to choose according to the capacity of photovoltaic, under normal circumstances the specifications are 100KW, 200KW, 400KW. The selection of disturbance resistance should also be selected according to the specification. The main selection parameters are resistance value, rated current, short-time tolerance current, tolerance time and so on.

Operation switch: Time delay protection: low voltage anti-islanding device should have time delay protection function. When the low-voltage anti-islanding device is mistakenly put into operation, the circuit breaker should be immediately switched off. When the anti-islanding function fails, the circuit breaker should be switched off through the delay device to ensure that the disturbance resistance is not damaged. The delay protection parameter can be set. The delay protection action time is set to 1S. The overload protection action time should fully consider the disturbance resistance characteristics, and the delay protection deviation should not exceed 100ms.

Interlock function with upper and lower voltage circuit breakers: The operating switch of the low voltage anti-islanding device should be compatible with the upper and lower voltage circuit breaker installed, and the interlock function should be designed to ensure that the anti-islanding device can be put into use only after the upper circuit breaker is disconnected. Mechanical or electrical interlock mode should be adopted

Rx-9390k load special controller: This controller controls the input of disturbance resistance, and at the same time with the superior switch for electrical locking, only when conditions are met, can be closed anti-island switch, input disturbance resistance. When the conditions are not met, it cannot be invested, and it cannot be automatically invested in anti-island. Therefore, in order to avoid miscasting anti-island, manual input is prohibited. When the superior anti-island switch has no available locking point, it can only be manually closed after confirming that the superior switch is in the off state.

Protection configuration function of anti - island device

1. Low frequency protection: when the frequency is between 35HZ-65HZ and has been above the low frequency value, the low frequency protection can be started. The low frequency protection action will be returned immediately after 200ms.

2, overfrequency protection: when the frequency is higher than the fixed value, the protection starts.

3, low voltage protection: when the voltage is lower than a fixed value.

4, overvoltage protection: when the voltage is higher than the fixed value.

5. Connection jump: support substation side connection jump, that is, when the substation side connection jump command is received, the trip exit is delayed and the grid-connected switch of the station is cut.

6, frequency mutation: when the frequency fluctuation value exceeds the set value, the protection action.

The main function of anti-island protection device

Function 1: When the power grid side is out of power, maintenance personnel need to repair, then the photovoltaic side is still in the normal state of power generation, but also to the power grid side, at this time will form an island effect, to the power grid side maintenance personnel brings great safety threat. Similarly, when the photovoltaic side of the failure, the need for personnel maintenance, and the power grid side, so that the power grid side may be back to the site, will also bring the photovoltaic side of the maintenance personnel life safety risks. If the anti-island device is installed, when the photovoltaic side or any side of the grid side loses power, the anti-island protection device will quickly issue a command to the grid-connected switch, so as to make it trip, so as to ensure the life safety of maintenance personnel on both sides of the photovoltaic.

Function 2: When the frequency, voltage or overload operation of the photovoltaic side or any side of the grid side causes impact to the main equipment on both sides, the anti-island protection device will also quickly issue a command to the grid-connected switch, so as to make it trip, so as to ensure that the main equipment on both sides is not harmed and avoid further expansion of the accident.

Function 3: Intelligent grid-connection: The device has the functions of loss of voltage trip and automatic closing of voltage detection. When the fault is removed, both sides of the photovoltaic are in normal state. At this time, the anti-island protection device will detect the relevant signal, and automatically close the grid-connected switch, so that it can work normally, saving the tedious manual grid-connected.

What functions should island protection devices have?

First, must be on the function

overfrequency

underfrequency

overvoltage

Low voltage

Frequency mutation

Inverse power

External jump

Abrupt frequency changes lock in low frequencies

System power loss

Automatic closing under pressure

Two, optional functions

Quick break

Direction lock speed break

Limit speed break

Direction lock limit speed break

overcurrent

Directional blocking overcurrent

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