Parallel Connection and Scheme of High-voltage Generator Sets

What is a parallel diesel generator?

Parallel operation of diesel generator means that two or more gensets with the same or different power (or single unit and main power supply) operate, and its output cable is connected to a single electrical bus. The process of parallel operation of diesel generator is called synchronization. Synchronous generators involve matching the frequency and voltage waveforms of each unit before closing the output circuit breaker to combine the power supplies together.

Parallel diesel generator will not normally be attempted when out of sync. After completion, all parallel power sources (whether they are the main power source or the generator) must be synchronized immediately.

Why use diesel generator in parallel?

Diesel generator are used in parallel to increase the overall system size and increase redundancy. It may also be more cost-effective to combine several smaller diesel generator over one larger diesel generator.

High-voltage diesel generator set operates in parallel

The entire process of putting a generator set into parallel operation is called parallel operation. One generator set is first put into operation, and the voltage is sent to the bus. After the other generator set starts, it is parallel to the previous generator set. At the moment of closing, the generator set should not have harmful impact currents, and the shaft should not be suddenly impacted. After closing, the rotor should be able to be quickly pulled into synchronization, so the paralleling of generator units must meet the following conditions:

1.The effective value and waveform of the generator set voltage must be the same.

2. The voltage phases of the two generators are the same.

3. The frequency of two generator sets must be the same.

4. The phase sequence of the two generator sets is consistent.

Typical scheme of high-voltage diesel generator set

Such as 6.3KV or 10.5KV high voltage diesel generator set. It consists of N generator set incoming cabinets, N generator set outgoing cabinets, N generator set neutral point cabinets, 1 busbar PT cabinet, 1 set of automatic parallel control screen (touch screen, automatic parallel, manual synchronization), 1 set of DC screen, 1 set of low-voltage power box, etc.

The automatic parallel system has a programmable controller as the command core, and the parallel instrument is the executor of parallel and load distribution. The high-voltage distribution unit is the distribution unit, and the parallel instrument collects the three-phase voltage of the engine (sampled by the high-voltage PT), the three-phase voltage of the busbar (sampled by the high-voltage PT), and the three-phase current of the generator (sampled by the CT). The automatic parallel controller provided in this plan is a Danish DEF-GPG fully digital controller. The system can achieve automatic start, automatic input, automatic parallel, automatic frequency regulation and load adjustment, automatic backup redundancy control, automatic withdrawal, automatic shutdown, automatic protection and other control functions. Microcomputer monitoring can be achieved through RS485 interface or RS232.

To increase reliability, a manual quasi synchronous parallel operation function is installed to achieve manual synchronous parallel generation of n generator sets. Manual quasi synchronous parallel operation is equipped with a synchronization meter (with synchronization pulse). When the parallel phase angle, voltage amplitude difference, and frequency amplitude difference meet the parallel conditions, the closing synchronization pulse signal is output. When the automatic adjustment device is activated, manual accurate adjustment will lock.

Dingbo Power company can supply diesel generator with parallel operations, if you have plan to purcahse diesel generators, welcome to contact us by email dingbo@dieselgeneratortech.com or call us by 008613481024441, we will reply you at any time.