The function of the main switchboard is to control and monitor the working condition of the diesel generator and supply power to the electrical equipment. The electrical instruments installed on the main switchboard are similar to the diesel generator control panel, except that the diesel generators do not need to run in parallel and do not need reverse power relays and synchronous meters. The main distribution board of the power supply system is generally composed of the control panel of the diesel generator set, the parallel panel, the load panel and the connecting busbar.
When the backup power supply and emergency power supply share the diesel generator set, it must comply with the regulations that the backup power supply and emergency power supply should have their own power supply bus sections and circuits; the power load of the backup power supply should not be connected to the regulations of the emergency power supply circuit. When the fire-fighting load and non-fire-fighting load of a civil building share the diesel generator set, the following regulations shall be met: the fire-fighting load shall be equipped with a professional circuit; it shall have the function of cutting off the non-fire-fighting load in the event of a fire; it shall have an alarm or display for low oil storage Function.
Composition of the main distribution board
1. Generator Control Panel
Generator control panels are used to control, regulate, monitor and protect generator sets. Each generator has its own control panel. The upper part of the control panel is equipped with ammeter, voltmeter, frequency meter, three-phase power meter and power factor meter (or kvar meter) of the generator, which are used to monitor the operating parameters and load status of the generator. There are three-phase measurement changeover switches under the voltmeter and ammeter respectively, which are used to check the symmetry of the three-phase current and voltage. In the middle of the panel are the closing and tripping buttons of the main switch of the generator, the manual closing handle (some are installed in the panel), and the speed regulation operation switch of the prime mover (used to adjust the frequency of the generator). The main switch of the generator is a frame-type universal air circuit breaker, which is installed inside the screen, which is both a switch and a protection device for the generator. There are instrument current transformers, voltage transformers and reverse power relays inside the screen. If there is no dedicated parallel screen, install the synchronous meter, synchronous light and its changeover switch for the entire step of paralleling on the control panel in the middle of each generator control panel.
2. Parallel screen
For those with more generator sets and a larger main switchboard, a special parallel screen is provided for the convenience of parallel operation. Install the synchronization meter, synchronization indicator light and its changeover switch on the panel of the parallel screen. It is also equipped with a frequency meter and its transfer switch for detecting the frequency of the power grid and the parallel machine. At the same time, the speed control switches, closing and tripping buttons of each generator are also installed on the parallel panel, which can be operated separately on the control panel and the parallel panel. The parallel system should be equipped with a first start detection system, the principle of which is as follows: After receiving the mains power outage dry contact signal, the generator system will start all generator sets, when any first one reaches 90% voltage and 90% frequency When the generator starts the first start detection system, it will prohibit other generators from closing to the empty bus. When the bus is energized, other generator sets can be paralleled and combined with the brake at the same time. The start-up and parallel operation of the whole system are completed within about 30 seconds, which has a very fast response speed.
3. Load screen
The load screen is used to distribute electric energy, and to control, monitor and protect each feeder line. Each feeder line is equipped with an automatic switch on the load screen for control and protection. Most of these automatic switches are device type (or plastic case type) automatic air circuit breakers. There is always an ammeter on the load screen, and the load current of each feeder line can be measured through the transfer switch.
4. Busbar (or connecting busbar)
It is the common connection conductor for all screens of the main switchboard. Three flat copper bars installed inside the main switchboard and across the main switchboard. They are A (green), B (yellow), and C (brown) three phases of AC. Some busbars are divided into two or several sections by the isolating switch, disconnecting the isolating switch can carry out power failure maintenance of some equipment without interrupting the power supply of important equipment.