The equipment with high fire risk in photovoltaic power station includes junction box, inverter, storage battery, connector, power distribution cabinet, transformer, etc., which is prone to electrical fire. The main buildings of photovoltaic power station are comprehensive control room and distribution station. For substations with a voltage above 35kV and a single transformer capacity above 5000kV˙ A, the transformer scale belongs to the application scope of GB50229-2006 Code for Fire Protection Design of Thermal Power Plants and Substations [1] (hereinafter referred to as Code for Thermal Power Generation), and its fire protection design can be implemented with reference to this code.
According to the building characteristics of photovoltaic power plants and the Code for Thermal Power Generation, the fire hazard classification and fire resistance rating of buildings (structures) of photovoltaic power plants are shown in table 1 [1]. When the cable interlayer cable adopts Class A flame retardant cable, its fire risk can be Class D; When no measures are taken to prevent cable extension after the fire in the comprehensive control room, the fire risk should be Class C; Power distribution equipment buildings and outdoor power distribution equipment determine the fire risk according to the oil content of the equipment.
2, fire prevention measures
According to the Code for Thermal Power Generation and the characteristics of electrical equipment in photovoltaic power plants, the following fire prevention measures should be taken in photovoltaic power plants:
2. 1 general layout
The location of photovoltaic power station should be based on the national medium-and long-term development plan of renewable energy, solar energy resources, access to power grid, environmental protection and other factors, and the fire spacing between internal buildings (structures) and external buildings (structures), yards and storage tanks of the power station should comply with the provisions of building codes. The fire lanes of large and medium-sized photovoltaic power stations should be arranged in a ring shape. When it is the end lane, a return yard or lane should be set.
2.2 Fire prevention measures for transformers and other oily electrical equipment.
(1) Because oily electrical equipment is easy to cause fire during use, in order to prevent the fire from spreading to adjacent buildings, a firewall should be set on the side adjacent to other buildings (structures) [1].
(2) Electrical equipment with indoor total oil content exceeding 1000kg and electrical equipment with outdoor total oil content exceeding1000 kg shall be provided with oil storage or oil retaining facilities, and cobble layers shall be laid in the oil storage facilities [1].
2.3 Cable fire prevention measures
Because the photovoltaic power station occupies a large area and cables are widely distributed, it is impossible to set a fixed cable fire extinguishing device. Fire-proof separation and flame-retardant cables should be adopted in cable trench as the main measures to deal with cable fire, and cables laid in trench and trough box should be flame-retardant cables of grade C or above.
2.4 photovoltaic power plant operation and maintenance safety
(1) Operation and maintenance personnel should have corresponding professional skills. Before maintenance, safety preparations must be made, and all switches that should be turned off should be turned off to ensure the complete discharge of capacitors and inductors. Wear insulating shoes, low-voltage insulating gloves and insulating tools when necessary. After the work is completed, the possible accidents in the system should be eliminated.
(2) Due to the particularity of components, voltage will be generated when receiving radiation. High-voltage direct current is formed after photovoltaic arrays are connected in series, which will cause serious safety accidents if they are not careful to form a loop with human body. Generally, before the photovoltaic array is connected to the system, the assembly string should be kept open, and after the photovoltaic array is connected to the system, the junction box (box) switch should be turned off. During the construction process, photovoltaic modules should be shielded by shields. When it is difficult to shield, the construction personnel should be equipped with safety protection articles to ensure safety.
(3) In order to prevent equipment overheating, short circuit and other accidents, flammable and explosive articles shall not be piled around the main components of photovoltaic power station.
2.5 Fire fighting facilities
2.5. 1 The planning and design of the fire-fighting water supply hydropower station should design the fire-fighting water supply system at the same time, and the fire-fighting water source should be reliably guaranteed. Fire water supply should be calculated according to the sum of indoor and outdoor fire water consumption with the largest fire water consumption at one time. The following conditions shall not be set:
(1) The photovoltaic plaza area (including the inverter booster room) should not be equipped with a fire water system. The photovoltaic array area is mainly composed of electrical equipment, and the DC side is always charged during the day, which is not suitable for fire extinguishing with water.
(2) According to the Code for Thermal Power Generation, there is no need to set fire hydrants in the outdoor distribution equipment area of substation (except the main transformer fire hydrant with water spray) [1].
(3) According to the provisions of the building code, when the fire resistance rating of buildings in the power station is not less than Grade II, the volume is not more than 3000m3, and the fire risk is Class E, indoor and outdoor fire water condensation is not required [2].
The volume of single building of ground photovoltaic power station is generally less than 3000m3, and the monitoring system is fully functional, with few personnel on duty and scattered buildings. Large-scale ground photovoltaic power plants are generally built in arid and water-deficient northwest desert areas. Domestic water is mostly transported by car, and the water cost is high, so it is difficult to set up a water fire fighting system.
Automatic fire extinguishing facilities
According to the Code for Thermal Power Generation, a single main transformer with a capacity of 125mv A or above should be equipped with water spray fire extinguishing system, synthetic foam spray system or other fixed fire extinguishing devices. Other electrical equipment with oil should use dry powder fire extinguishers [1].
Oil-immersed transformer oil has good insulation and thermal conductivity. The flash point of transformer oil is generally 130℃, which is a flammable liquid. When the internal fault of the transformer occurs arc flashover, and the oil is decomposed by heat to generate steam to form a fire, it is necessary to set up automatic fire extinguishing systems such as water spraying. In areas with water shortage, cold, windy sand and harsh operating conditions, oil drainage and nitrogen injection fire extinguishing devices and synthetic foam spray fire extinguishing systems can be selected, and transformers in indoor enclosed spaces can also use gas to extinguish fires. For small and medium-sized substations, the cost of automatic fire extinguishing system is relatively high, and fire extinguishers can be used.
automatic fire alarm system
The fire hazards of photovoltaic power plants are mainly cables and electrical equipment. Because the power generation of photovoltaic power plants is determined by solar radiation, the load of electrical equipment and the current carrying capacity of cables also change with the change of solar radiation, which is zero in the morning and evening and close to the design value at noon, so the fire probability of photovoltaic power plants is much smaller than that of conventional thermal power plants. According to the Code for Thermal Power Generation and the characteristics of photovoltaic power plants, large photovoltaic power plants or unattended power plants can be equipped with fire alarm systems. Smoke fire detectors can be used in main control room, relay equipment room, reactive power compensation room and power distribution equipment room, and linear temperature fire detectors can be used in main transformer (indoor), cable layer and cable shaft.
2.5.4 Fire power supply, emergency lighting and fire extinguishers
In order to ensure the safety of fire fighting power supply and the normal operation of fire fighting system, fire pump, fire alarm and fire emergency lighting are supplied with power according to the secondary load, fire emergency lighting and evacuation indication signs are set in the main control room and distribution equipment room of the power station, and the power station is equipped with fire extinguishers according to the requirements of GB 50 140-2005 Code for Design of Fire Extinguishers in Buildings.