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What is the power distribution equipment system? How to debug the power distribution equipment system
**First, Introduction to the Power Distribution Equipment System**
In power engineering, terms such as "distribution room," "distribution cabinet," and "distribution box" refer to devices used for measuring and controlling electrical energy. These systems typically consist of busbars, switchgear, protective devices, and measuring instruments. The layout must meet operational requirements, be easy to maintain, and ensure the safety of personnel and surrounding equipment. They are commonly found in power plants, distribution stations, and similar facilities.
The electrical distribution boxes or panels in the power distribution system may not have any adjustable components, meaning no commissioning is required. However, if each user room's distribution panel includes electromagnetic switches, leakage protectors, or other adjustable elements, and the manufacturer has already set them according to standard parameters, then no further commissioning is needed by the installation team. In such cases, the commissioning cost should not be included. For systems that require post-installation commissioning, the construction unit must perform it following technical specifications, record the process, and calculate the cost accordingly.
During the bidding phase, since electrical equipment like distribution boxes may not yet be ordered, it can be difficult to determine whether commissioning will be required. This ambiguity can lead to confusion in pricing and bids. Therefore, for bidding projects, it is recommended that the commissioning cost for systems with adjustable components be temporarily estimated in the budget and clearly stated in the contract. Adjustments can be made during project settlement based on actual conditions. Electrical commissioning is a complex task requiring high professional standards, and it is essential to take the cost seriously while striving to master the necessary skills.
**Second, Content of Electrical Commissioning for the Power Supply and Distribution System**
Electrical commissioning for power distribution systems involves both the primary and secondary circuits. This includes testing circuit breakers, isolating switches, current transformers, reactors, and the secondary circuits for relay protection and measuring instruments. The commissioning process typically covers general-purpose relay protection devices, such as overload and short-circuit protection, but does not include special protection systems or automatic device adjustments.
Commissioning for transmission and distribution equipment applies to busbar connections, busbar sections, and circuit breaker circuits. If busbar protection is installed, the busbar section breaker circuit must be commissioned separately. Additionally, the commissioning of 380V and 3–6kV motor feed circuits is included in the motor inspection and commissioning list. Transformer incoming lines are not considered part of the power distribution system; instead, their commissioning is included in the transformer system.
For high-voltage power distribution systems in factories, the power supply line is quoted from the 6kV main distribution busbar (if no transformer is used), and the commissioning of the power distribution system is listed separately.
**Third, Commissioning Instructions for Transmission and Distribution Systems**
Power distribution systems are commissioned based on the number of circuit breakers that meet specific criteria. A unit project must include at least one loop of the power supply system for commissioning. The criteria include:
1. Circuit breakers with a rated current of 100A or higher.
2. Not being transformer high/low side circuit breakers or internal cabinet circuit breakers.
3. Not just maintenance isolation switches without protection functions.
Commissioning below 10kV includes power supply circuits from the distribution device to the distribution box. However, the power supply from the distribution box to the motor is included in the motor system commissioning. The commissioning process includes cable tests, insulation resistance checks, and testing of circuit breakers, relays, and measuring instruments.
General instruments and protection transformers are included in the corresponding power distribution system commissioning. Metering instruments and transformers are verified by the power supply department, and their costs are accounted for accordingly. Switchgear and cable tests are already included in the commissioning sub-item, so no additional calculation is required. Motor-powered cable and switchgear tests are included in the motor system commissioning. Dense busway commissioning is also included in the power distribution system, while busway between cabinets is included in the busbar commissioning.
Each circuit breaker on one side counts as one system. If there are circuit breakers on both sides, it is calculated as two systems. Power distribution systems are suitable for various power supply circuits, including lighting loops. If a power supply circuit contains adjustable components like instruments, relays, or electromagnetic switches, it is counted as a commissioning system. Devices pre-adjusted by the manufacturer and not requiring user adjustment, such as mobile appliances or household sockets, are not included.
**Fourth, How to Commission the Transmission and Distribution Equipment System**
1. High-voltage power distribution cabinets are calculated based on the number of sets used, with the quota professionally determined.
2. Low-voltage power distribution cabinets are not individually counted but are included in the commissioning quota below 1kV. This includes all low-voltage power supply circuits, such as from the distribution equipment to the distribution box. Circuits from the distribution box to the motor are included in the motor system commissioning.
The commissioning process includes full-system tests, such as cable testing and porcelain bottle pressure resistance. Circuit breakers and busbar section breakers in the power supply bridge circuit are considered independent power supply systems. The quota is calculated based on one circuit breaker per side. If there are breakers on both sides, it is counted as two systems. If only a power supply circuit with a knife switch, fuse, or air switch without any adjustable components is present, it is not counted as a commissioning system.