The startup/standby power supply of Shuidonggou Power Plant comes from the 1 10kV bus of the nearby Xujiazhuang 330kV substation. The scheme of installing generator outlet circuit breaker and small capacity standby shutdown transformer is adopted. The power supply for normal start-up and shutdown of the unit is sent back by the factory 750kV bus, and the standby power supply for shutdown is provided by the shutdown transformer.
1.2 system introduction
1.2. 1 main electrical wiring
According to the report of power plant access system, two 660MW units are connected to the 750kV booster station in the plant through the generator outlet circuit breaker and booster transformer, and the 750kV outgoing line is connected to Yinchuan East 750kV substation twice in this period. In this phase, the 750kV power distribution equipment adopts the open layout scheme, and the 750kV outgoing lines of two machines, two transformers and two circuits are connected by one and a half circuit breakers, and two complete strings are set.
Two machines in this project are equipped with an on-load voltage-regulating double-winding shutdown transformer with a capacity of 3 1.5MW, and a circuit breaker is installed at the generator outlet. The power supply for normal start-up and stop of the unit is sent back by the factory 750kV bus, and the standby power supply for stop is provided by the stop transformer. The power supply of the stopped transformer comes from Xujiazhuang 330kV substation 1 10kV bus.
1.2.2 voltage transformer configuration
Each group of 750kV buses is equipped with a set of voltage transformers; Each 750kV outgoing line is equipped with a set of voltage transformers; Each main transformer incoming loop is equipped with a set of voltage transformers; Each generator outlet loop is equipped with three sets of voltage transformers, two of which are completely insulated and one is semi-insulated.
1.2.3 current transformer configuration:
Each phase at the generator outlet and neutral point side is equipped with 4 sets of jacketed current transformers.
Each phase of the high voltage side of the main transformer is equipped with 4 sets of casing CT. The neutral point is equipped with two current transformers.
Each 750kV circuit breaker is equipped with 8 sets of jacketed current transformers.
The high-voltage side of the high-voltage auxiliary transformer is equipped with 5 sets of jacketed current transformers.
The high voltage side of the high voltage utility transformer is equipped with 5 sets of casing CT.
There are 3 sets of jacketed current transformers on the high voltage side of the shutdown transformer.
1.2.4 arrester configuration
750kV incoming and outgoing lines and two buses are respectively provided with a set of lightning arresters; 1 10kV incoming cable is equipped with two sets of lightning arresters, and outgoing cable is equipped with one set of lightning arresters.
A lightning arrester is installed at the outlet of each generator.
Each generator outlet circuit breaker is equipped with a set of lightning arresters near the main transformer side.
1.2.5 750kV lightning arrester and voltage transformer are not equipped with disconnectors.
1.2.6 grounding mode of neutral point voltage at all levels
The neutral point of the generator is grounded through a single-phase transformer with secondary resistance (with middle tap).
The 750kV system is directly grounded, and the neutral points of three single-phase transformers are not grounded. 1 10kV system is an effective grounding system, and the neutral point on the high voltage side of the shutdown transformer is grounded through an isolating switch.
1.2.7 auxiliary power system
1.2.7. 1 The high-voltage auxiliary power voltage is 6kV primary voltage, and its neutral point is grounded with low resistance.
1.2.7.2 The high-voltage auxiliary power system adopts the scheme of setting public sections.
Each machine is equipped with 50/3 1.5-3 1.5MVA on-load voltage-regulating high-voltage service transformer (with split winding) and 25MVA on-load voltage-regulating high-voltage service transformer (with double winding transformer). The high-voltage side power supply of the auxiliary high-voltage transformer and the public transformer is connected by the closed bus between the generator and the main transformer of this unit. Each unit is equipped with two sections of 6kV working bus and one section of 6kV public bus. The unit load is connected to sections A and B of 6kV service transformer of high-voltage auxiliary transformer, and the public load of the whole plant is connected to sections A and B of 6kV public transformer of two high-voltage auxiliary transformers. The high-voltage auxiliary motor and low-voltage auxiliary transformer, which are mutually standby and appear in pairs, are connected by different 6kV working sections respectively.
A shutdown transformer with a capacity of 3 1.5MVA is set in this project, and the shutdown transformer adopts an on-load voltage-regulating double-winding transformer. The 6kV side of the shutdown transformer is connected to four sections of 6kV working bus and two sections of 6kV public bus through the * * box bus as standby shutdown power supply.
The capacity selection of shutdown transformer is based on the capacity required to meet the normal shutdown of the machine.
There are a large number of high-voltage motors in the coal conveying system of this project, and the arrangement position of 6kV power distribution devices in the main workshop is limited, so a 6kV coal conveying section is set in the coal conveying complex. There are two 6kV coal conveying sections in this project, and the two buses are connected by the 6kV public section of two machines, which are used as backup for each other. Automatic switching device of coal conveying equipment in section A and B.
1.2.7.3 Electrical wiring of desulfurization system
The desulfurization system of this project adopts EPC general contracting method.
The desulfurization system is powered by high and low voltage, the 6kV desulfurization load is powered by the 6kV bus section of the main building, and the 380V desulfurization load is powered by two low-voltage transformers in the desulfurization island. The security power supply of desulfurization island is provided by the main workshop, once for each unit. The desulfurization island is equipped with 1 10V DC split screen, and its DC power supply is provided by the DC system of the main building, with two circuits for each unit.
1.2.7.4 the voltage of the low-voltage auxiliary power system is 380/220V.
The low-voltage auxiliary power system adopts neutral point direct grounding mode, and the low-voltage auxiliary bus is single bus configuration.
Each unit is equipped with a steam turbine and boiler distribution center in the main building, which consists of two 1600 kVA steam turbines and two 2500 kVA boilers to supply power to the low-voltage load of the unit's 380V boilers and auxiliaries.
Each unit is equipped with a lighting power supply center, which is powered by 1 800 kVA lighting transformer, and the two lighting transformers are mutually standby.
Two machines are equipped with a public power center, and the capacity of the public transformer is 2000kVA, and the two public transformers are mutually standby.
There is no special maintenance transformer in this phase, and each unit is equipped with ventilation maintenance MCC.
Each unit is equipped with a security power center, and each unit is equipped with a 1250kW diesel generator set.
The auxiliary workshop is equipped with 380/220V power center according to the load distribution, and the settings are as follows:
Power center, each furnace is equipped with two power transformers with a capacity of 2500kVA and two PC buses (equipped with automatic equipment switching devices); Set a special standby transformer for electrostatic dust removal with the same capacity.
Water treatment power center, two 2500kVA transformers, which are standby for each other, and the power center is equipped with two buses.
Two 1600kVA transformers are set in the power center of coal transportation, which are standby for each other, and two buses are set in the power center.
The power center of dumper is equipped with two 1250kVA transformers, which are standby for each other, and the power center is equipped with two buses.
The ash removal power center is equipped with two 2000kVA transformers, which are standby for each other. The power center is equipped with two buses.
The factory power center is equipped with two 630kVA transformers, which are standby for each other, and the power center is equipped with two buses.
The motor control center (MCC) of the main building is distributed according to the load. Paired motors are powered by two MCC sections respectively, and a single auxiliary motor is powered by two MCC sections. Some important MCC parts are automatically switched by dual power supplies.
The motor control center (MCC) of the auxiliary workshop adopts the MCC section with double power supply according to the load distribution.
The motor with the capacity below 75kW and the static load below 200kW are powered by MCC, and the low-voltage motor with the capacity above 75kW and the static load above 200kW are powered by the power center.
Indirect cooling tower load power supply
The 380V cooling tower load of indirect cooling system is powered by the 380/220V MCC section in the cooling tower of each unit, and the circulating water pump room load is powered by the 380/220V MCC section of the circulating water pump room of each unit, and the power supply comes from the water treatment low-voltage transformer.
1.2.7.5 main building DC system
Each machine is equipped with three sets of batteries, including one set of 220V power batteries and two sets of 1 10V control batteries.
1 10V control battery pack adopts single bus sectional wiring; The 220V power battery pack adopts single bus configuration, and the 220V power battery packs of two units are connected by cables.
1 10V control DC system is used to control, protect, measure and other control loads. 1 10V control DC system adopts radiation network power supply mode, and each distribution room is provided with DC split screen.
220V DC power system provides emergency lighting, power load and AC uninterrupted power supply.
The battery pack usually operates in a floating charging mode. All types of batteries are valve-controlled maintenance-free lead-acid batteries.
1 10V control battery configuration: two sets of 800Ah batteries, corresponding to two sets of high-frequency power supply devices. The high-frequency power supply module adopts N+2 redundancy configuration.
220V power battery configuration: one set of 2000AH battery and one set of corresponding high-frequency power supply equipment. The high-frequency power supply module adopts N+2 redundancy configuration.