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What are the common DC power systems | with solutions

What are the common DC power systems | with solutions

  • Categories:Company news
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  • Time of issue:2020-06-17
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(Summary description)DC power supply systems are widely used in various power plants, substations and other power system core hubs

What are the common DC power systems | with solutions

(Summary description)DC power supply systems are widely used in various power plants, substations and other power system core hubs

  • Categories:Company news
  • Author:
  • Origin:
  • Time of issue:2020-06-17
  • Views:0
Information

Introduction to DC power system composition and function

The DC power supply system is widely used in various power plants, substations and other power system core hubs. The power supply network is composed of battery packs, charging devices, DC feeder panels, DC power distribution cabinets, DC power monitoring devices, DC branch feeders, etc., to protect relays Various subsystems such as device, circuit breaker tripping and closing, signal system, DC charger, UPS, communication, etc. provide safe and reliable working power.

As the core equipment of the substation, the DC power supply system of the substation provides power to the control equipment of the substation. If the power supply is stopped due to a fault, it will directly affect the normal operation of the substation. For a long time, the DC power supply system of substations has been continuously developed and improved. At present, most of the chargers use high-frequency switching power supplies. The batteries have also been upgraded from the original acid-proof lead-acid batteries to valve-regulated sealed lead-acid batteries, and are equipped with DC Power supply computer monitoring device.

The main functions of the battery pack in the operation of the DC power supply system:

1) When the mains power is interrupted or the DC charging equipment fails, the battery pack supplies power to the load separately to ensure uninterrupted power supply.

2) Under the short-circuit impact of the load or the initial impact of normal load, the part that exceeds the rated output of the charger is borne by the battery.

3) Smooth filtering. The battery pack has the same charging and discharging function as the capacitor, isolating the AC components, so that the AC components sent to the load are further reduced, and the load's requirements for voltage quality are guaranteed.

Daily regular inspection contents and common faults of battery packs:

1) The valve-controlled battery pack operates in a floating charging mode during normal operation. The single float charging voltage value should be 2.23-2.28V, and the equalizing charge should be 2.3-2.35V. The terminal voltage value of the battery pack should be monitored during operation. Floating charge current value, single battery voltage value, ground resistance and insulation state of battery pack and DC bus.

2) Daily periodic inspection of battery packs: actual terminal voltage measurement, internal resistance test, dynamic discharge test, and AC input power switching test for charging devices.

3) Function of valve-controlled battery safety valve: The valve-controlled battery is in a sealed state under normal charging and is equipped with a safety valve that can automatically open and close. When the internal pressure exceeds the specified opening threshold, the safety valve automatically opens, and when the pressure is lower than the closing threshold, it automatically closes. The safety valve is equipped with an acid filter device, which will not discharge harmful gases such as acid mist, and will not leak electrolyte, which can prevent sparks from causing battery explosion.

4) Common faults of valve-controlled batteries: abnormal valve-controlled battery shell, abnormal valve-controlled battery discharge voltage.

Charging device protection function and operation monitoring

The charger shall have the functions of over-voltage, over-current, under-voltage, DC insulation monitoring, AC loss of voltage, AC lack of equal protection, and sound and light alarm. The daily inspection work of the charger is indispensable, such as: whether the three-phase AC input voltage is balanced or lack of phase, whether the operating noise is abnormal, whether the protection signals are normal, the AC input voltage value, the DC output voltage value, the DC output current value, etc. Whether it is correct, whether the ground insulation is in good condition, etc. If the AC power supply is interrupted, the battery pack will supply power to the load uninterruptedly. If there is no automatic voltage regulating device, manual voltage regulation should be carried out to ensure that the bus voltage is stable and the AC power supply is restored. The charging device should be started manually or automatically immediately.

2 Routine testing during maintenance of DC power supply system

After the installation of the DC power supply system, a handover acceptance test must be carried out before it is put into operation. The test project must meet the technical requirements and the 72-hour test run is normal. Main content of handover acceptance:

Insulation monitoring and signal alarm device
Withstand voltage and insulation test
Battery pack capacity test
Charge device steady current accuracy test
Charge device voltage stabilization accuracy test
Ripple coefficient test of charging device
DC bus continuous power supply test

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