The Complete Guide to Pad-mounted Substations

This article will summarize the classification of pad mounted substations, and analyze several advantages of pad-mounted substations, as well as the device model and meaning description, which is conducive to the reasonable selection of devices in pad-mounted substations during design.

The pad-mounted substation is also known as an outdoor complete substation or a prefabricated substation. It began to develop in Western countries such as Europe and the United States in the 1960s and 1970s. Due to its flexible combination, convenient transportation, migration, and installation, it is pollution-free and maintenance-free.

The high-speed railway power supply system adopts a variety of new technologies and new equipment to improve the reliability of power supply. Among them, pad-mounted substations are more and more widely used.

The pad-mounted substation is a small substation that provides power for inter-area communications, signals, disaster prevention and other equipment, and combines high-voltage primary equipment, transformers, low-voltage primary equipment and secondary meters in a single box for power supply and distribution.

Daelim has been producing and designing pad mounted transformers since 2006. The excellent quality has enabled our products to be used in more than forty countries around the world. Daelim’s transformers have passed EEE, CSA, ISO9001, ANSI C57.12.00, IEC60076 certification. Ensure that you are perfectly adapted to the local market when you use it. At the same time, daelim’s transformers can also provide you with customized services. Daelim’s pad mounted transformer has been adopted and selected by more than fifty bitcoin mines. It can save you a lot of electricity bills.

pad mounted substation in Daelim's factory

Table of Contents

What is the pad-mounted substation?

A pad-mounted substation belongs to a power distribution station, which provides power for railway yards and section load equipment. It is mainly composed of a combination of electrical components such as multi-loop switch systems, busbars, integrated automation systems, telecontrol, metering, and capacitor compensation.

The pad-mounted substation is installed in a dust-proof, waterproof, moisture-proof, heat-insulated, fully enclosed and movable steel structure box, which is divided into three parts: a high-voltage room, a transformer room, and a low-voltage room.

The pad-mounted substation mostly adopts front and rear layout to meet the safe operation conditions of indoor high and low voltage equipment.

What are the advantages of pad-mounted substation?

pad mounted substation

The pad-mounted substation is divided into a combined substation according to the structure. Its main advantages are:

① High reliability of power supply, electric mechanism, power distribution automation device and capacitor device can be added, which can reduce the loss of power supply line;

②It is convenient to increase the capacity. When the user needs to increase the capacity, the civil foundation can be reused, which greatly shortens the construction period;

③The pad-mounted substation has low radiation. Since the transformer is placed in the metal box, the box can play a shielding role. Due to the many advantages of pad-mounted substation, it is mostly suitable for more important building electricity.

What is inside of pad-mounted substation?

Pad-mounted substation is mainly composed of three parts. They are, high-voltage chamber, low-voltage chamber and pad mounted transformer. Next, I will tell you in detail The various parts of the pad-mounted substation and their functions.

inside of the pad mounted transformer
inside of the pad mounted transformer

parts of the pad-mounted substation: high pressure room

The high-voltage room of the pad-mounted substation is mainly composed of a 35kV or 10kV high-voltage incoming cabinet on the power supply side, a high-voltage outgoing cabinet, and a high-voltage metering cabinet.

The main equipment includes load switches, fuses, voltage transformers, current transformers, lightning arresters, etc. The model definitions of several major equipment are introduced below.

FV arrester

FV lightning arrester model meaning description

The main component of the high-voltage arrester is the spark gap, which is used to limit the atmospheric overvoltage and isolate the high-voltage wire from the ground. At the same time, it can also extinguish the power frequency freewheeling arc formed by the shock wave breakdown. It is widely used in railway transmission and transformation, power transformation, and power distribution systems to protect railway electrical equipment from overvoltage damage.

FU fuse

FU fuse model meaning description

The fuse is used as a protection element for short-circuit and overload of power transformers and other equipment. Because the high-voltage load switch can only cut off the load current, when it encounters short-circuit and overload conditions, the current becomes larger, and the load switch cannot cut off the current at this time. When encountering a large current, the fuse will cut off the large current.

Voltage transformer

PT: Description of the meaning of the voltage transformer model

The voltage transformer is based on the principle of electromagnetic induction to transform the high voltage into a standard secondary voltage of 100V or lower in proportion to the use of protection, metering, and instrumentation. At the same time, the use of voltage transformers can isolate high voltages from electrical workers.

Current Transformer

CT: Description of the meaning of the current transformer model

The function of the current transformer is to convert the primary current with a larger value into a secondary current with a smaller value through a certain transformation ratio, which is used for protection, measurement and other purposes.

parts of the pad-mounted substation: pad-mounted transformer

Pad mounted transformer is a static electromechanical device. It uses the principle of electromagnetic induction to convert one voltage and current alternating current into another or several different voltage and current alternating currents of the same frequency. It can realize the conversion of different levels of electrical energy. , It is an important electrical equipment to realize the conversion, distribution and use of electric energy.

  • Comparison of performances of transformers See Table 1 for performance comparisons of various transformers.
  • Choose transformers according to environmental conditions. There are many types of transformers. When selecting transformer types, the environmental characteristics of the place of use need to be considered. See Table 2 for the scope of application and comparison of various transformer characteristics.

Table 1

categoryOil-immersed transformerDry-type transformer
Mineral oil transformerSilicon oil transformerOrdinary winding dry-type transformerEpoxy resin cast transformer
Installation areamiddlemiddlesize)small
ExplosivepossibleUnlikelyNot burstNot burst
Moisture resistancegoodgoodweakexcellent
weightHeavyHeavierHeavy (light)light

Table 2

Transformer typeScope of applicationReference model
Ordinary oil-immersedSubstation in general environmentS9-S11, S15, S9-M type distribution transformer
DryUsed in substations with high fire protection requirements or humid and dusty environmentsSC(B)9-SC(B)11 series epoxy resin cast transformer
SealedUsed in places where chemical corrosive gases, combustible dust, and fibers will affect the operation of the transformerS9-M, S11-M, R type oil-immersed transformer
Lightning protectionUsed in minefields and mountainous areas with high soil resistivitySZ series lightning protection transformer

parts of the pad-mounted substation: low pressure room

The low-voltage room of the pad-mounted substation is mainly composed of a low-voltage incoming cabinet, a low-voltage outgoing cabinet, and a low-voltage compensation cabinet. The main equipment includes voltage and current meters, power factor meters, isolation switches, circuit breakers, lightning arresters, etc. The following describes the main equipment Model meaning.

  • The meaning of current, voltage, power, and power factor model descriptions. Current, voltage, power, and power factor are mainly monitored by various high and low voltage switch cabinets, power cabinets, control cabinets and various electric control devices.
  • QF low-voltage circuit breaker model meaning description Low-voltage circuit breaker, also known as low-voltage automatic switch, is a switch with protection device, which can automatically cut off the circuit when overload, short circuit and undervoltage fault occurs in the load circuit. Commonly used low-voltage circuit breakers include frame type circuit breakers, plastic case type short-circuiters, intelligent circuit breakers, fast circuit breakers and current-limiting circuit breakers.
  •  The meaning of the QS isolating switch model indicates that ordinary isolating knife switches cannot be operated with load. By using it in conjunction with a circuit breaker, the isolating switch can only be operated after the circuit breaker cuts off the circuit. The knife switch acts as a power isolation switch, resulting in an obvious disconnection point. , To ensure the safety of maintenance personnel. Mainly used in the control circuit of power distribution equipment, for infrequently electric connection and cut-off or isolation of the power supply, the operation should be carried out under no load.

Concluding remarks

daelim 1250 kva pad mounted transformer

With the increasing application of pad-mounted substations in railways, the accuracy and reliability requirements of pad-mounted substations are getting higher and higher, and higher requirements are put forward on the distribution network and power supply equipment.

The pad-mounted substation is more and more affirmed by the society for its advantages such as small area, rapid installation, convenient movement, and low investment. Its future development trend is to form a smaller-scale unattended substation.

In the process of power design, it is necessary to carefully select the models and installation methods of the primary equipment, transformers, low-voltage primary equipment and secondary instruments of the pad-mounted substation to improve the quality of the power engineering in the construction of passenger dedicated lines.

About Bin Dong

Hello, I am Bin, General manager of Daelim which is a leading transformer manufacturer. If you have problems when you are looking for the equipment, what you need to do is tell us.