I'll show you Santak's uninterrupted power supply.Due to the aging of the UPS system in a substation, the inter phase short circuit occurs. Fault current leads to fire in UPS power supply panel, which further leads to AC series DC, and breaks through the varistor in the measurement and control device, which leads to multi-point grounding of DC system, and eventually leads to power loss of backstage monitoring system and remote communication.
1. The role of UPS
UPS Chinese is "uninterruptible power supply". It is a kind of energy storage device, with rectifier and inverter as the main components. It provides constant voltage and constant frequency uninterrupted power supply for monitoring system, automation instrument, remote communication system and other equipment in substation.
The main functions of the UPS system are two aspects:
(1) As an AC power supply for important equipment, it can prevent sudden power failure of municipal power from affecting normal work and causing damage to equipment;
(2) Eliminate "power pollution" such as surge, instantaneous high/low voltage, wire noise and frequency offset, improve the quality of power supply, and provide high-quality power supply for computers.
2. Classification of UPS
There are three types of UPS systems: backup, interactive and online.
(1) Backup type: It has the functions of automatic voltage stabilization, power-off protection and so on. The conversion time is about 10ms. The AC output of the inverter is square wave. It has simple structure and low price.
(2) Interactive: with filtering function, strong anti-interference ability, conversion time less than 4 ms, inverters output to analog sine wave, the price is much lower than online;
(3) On-line mode: complex structure, perfect performance, continuous output of pure sinusoidal alternating current, can solve all power problems such as peak, surge, frequency drift, etc. High price, usually used in critical computer and network equipment and other rigorous power requirements environment.
3, the structure of UPS
UPS system in substation generally consists of three parts: power UPS host, bypass voltage regulator and output feeder cabinet.
The schematic diagram shows the usefulness of several important parts.
Rectifier: There are two main functions: firstly, AC is transformed into DC, which is filtered and supplied to the inverter; secondly, charging voltage is provided to the battery to play the role of a charger;
Inverter: convert direct current (DC) to alternating current (AC) and supply load.
Battery: UPS is used as a device to store electric energy, so that it can provide uninterrupted power supply for load after DC inversion when power loss occurs in the city. Its capacity determines the duration of its discharge (power supply).
Static switch: also known as static switch, is an AC switch composed of two SCR in reverse parallel. Its closure and disconnection are controlled by logic controller.
Isolation transformer, voltage regulator: In the input or output part, AC and DC are isolated. Besides isolation, voltage regulator also has the function of stabilizing voltage.
4, four operation modes of UPS
(1) normal mode of operation:
Under the normal AC power supply, the rectifier converts AC to DC, eliminates the "power pollution" in the municipal power supply, and charges the battery at the same time. The inverter is supplied to convert DC to AC and provide a more stable power supply to the load.
(2) power failure mode:
When the AC power supply is abnormal or the rectifier or reactor fails, the battery pack provides direct current to the inverters, so that the AC output will not be interrupted, thus achieving the function of protecting the load.
(3) standby power mode:
When the inverter is in abnormal condition, such as fuse fuse, short circuit and other faults, the inverter will be automatically cut off to prevent damage. If the bypass AC power supply is normal at this time, the static switch will convert the power supply to the bypass standby power supply for load use.
(4) maintenance bypass mode:
When UPS needs to repair or replace batteries and the load power supply can not be interrupted, the inverter switch can be cut off first, then the maintenance bypass switch can be activated, and then the rectifier and bypass switch can be cut off. AC power supply continues to supply AC load through maintenance bypass switch. At this time, maintenance personnel can safely maintain UPS.
5, some requirements of power system UPS
(1) Monitoring system and remote communication system are very important to substation, so the reliability of UPS system as power supply is also very high.
(2) The load of integrated self-contained system is mostly single-phase load, so most of the special UPS power supply for power system requires medium and small power UPS with three-phase/single-phase input and single-phase output, and its capacity is generally within the range of 60 kVA.
(3) the bypass static switch should have two working modes: automatic and manual.
(4) as the substation has 220V or 110V DC system, there is a DC charging screen to charge the battery. Therefore, the special UPS for electric power does not have batteries, and directly uses the DC system as the DC input of UPS, and does not need to have charging function.
(5) The DC input terminal of power special UPS generally requires backfilling noise suppressor, such as backstop diode, to minimize the impact of UPS on DC bus.
(6) the UPS power supply should have more than 40% of the power supply capacity after it is full of equipment. UPS after the AC power failure, the uninterrupted power supply duration is not less than 60 minutes.