Overview

Medium-voltage switchgear plays a key role in power distribution system. To fully satisfy customer’s needs, XuJi (Xiamen) Intelligent Switchgear Manufacturing Co. Ltd. successfully developed their SGC1 switchgear based on the most advanced international product technologies and taking into account also the special requirements from the State Grid Cooperation of China.

SGC1 air-insulated, metal-clad switchgear is jointly desgined by our very experienced switchgear and circuit breaker experts inside and outside China. The application of the most advanced international technology provides SGC1 excellent safety and reliablity performance. We have seriously consider all needs of our customers and therefore, our proudct can fulfill demanding requirements under all operating conditions and climatic ambient. It is suitable for different market sectors.

The series of SGC1 switchgear panels are developed independently by XuJi (Xiamen), which includes the width of 600mm, 800mm and 1000mm. Among those types, our company is the first one to develop such 600mm width SGC1 switchgears, the smallest in the like products equipped with high reliable embedded poles circuit breaker, which largely save floor space and civil construction cost. SGC1 T600 panels are especially applicable for real estate and small industry.

In addition to our unique expertise in product design and product quality management, we are also experts in project management and customer services.

Standards

The switchgear and the main apparatus contained in it comply with the following Standards:
IEC 60071 Insulation Co-ordination.
IEC 60470 High-Voltage Alternating Current Contactors and Contactor-Based Motor-Starters
IEC 62271 High-voltage switchgear and controlgear - Part 200: AC metal-enclosed switchgear and controlgear for rated voltages above 1 kV and up to and including 52 kV
IEC 60694 Common specifications for high-voltage switchgear and controlgear standards
IEC 62271 High-voltage switchgear and controlgear–Part 100:High-voltage alternating-current circuit-breakers
IEC 62271 High-voltage switchgear and controlgear– Part 102: Alternating current disconnectors and earthing switches
GB 3906-2006 Alternating-current metal-enclosed switchgear and controlgear for rated voltages above 3 kV and up to and including 35 kV
GB 11022-1999 Common specifications for high-voltage switchgear and controlgear standard
GB 1984-2003 High-voltage AC circuit breakers
GB 1985-2004 High-voltage AC disconnectors and earthing switches



Overview

Key technical data

SGC1 is a medium voltage metal-clad switchgear with metal enclosure, suitable for indoor installations. Metallic partitions segregate the compartments from each other and the live parts are air-insulated. The switchgear can be fitted with conventional instrument transformer and relays or innovative sensors and switch bay control units with control measurement and protection functions.

Degrees of protection

The degrees of protection of the switchgear conform with IEC 60529 Standards and GB 4208-1998 Standards. SGC1 switchgears are normally supplied with the following standard degrees of protection:
• IP4X for the enclosure
• IP2X for the partitions

Service conditions

The rated characteristics of the switchboard are guaranteed under the following ambient conditions:
• Minimum ambient temperature: – 15 °C
• Maximum ambient temperature: + 40 °C
• Maximum daily relative humidity: 95%
• Maximum monthly relative humidity: 90%
• Maximum altitude: 1000 m a.s.l.
• Highest Seismic Intensity: 8
• Presence of normal, non-corrosive and uncontaminated atmosphere.
Notes: For special operating conditions, please consult the manufacturer for recommendations.

Special considerations

If the switchgears operate at higher humidity or in fast-changing weather conditions, there is a risk of condensation. Therefore, the instruction below should be followed:
- After installation, the heaters must be switched on as soon as possible.
- The heaters shall be turned on once the switchgear is in standby or in service conditions.

Color of the external surfaces

RAL7035 Light grey. For any other color requirements, please specify when ordering.



Design

Functional units

Each SGC1 is composed of three power compartments and one low-voltage compartment, namely A circuit-breaker compartment, B busbar compartment, C cable compartment, D low voltage compartment The compartments are segregated from each other by metallic partitions.


Busbar compartment

The main busbars are made of copper or aluminum and can be rectangular or D-shaped depending on the current rating. The main busbars and the T-off busbars are protected by heat shrinkable tube as insulating material. A specially designed insulating cover on the busbar connecting points to ensure no life parts is exposed. The switchgear is equipped with bushings to prevent the fault arc to migrate from one busbar compartment to another. The main busbars supported by the T-off busbars and no supporting insulators are required for the main busbars to reduce the insulation breakdown probability.


Circuit-breaker compartment

The insulating spouts in the circuit-breaker compartment hold the fixed contacts for connecting the apparatus with the busbar compartment and the feeder compartment respectively. They are made of epoxy resin. The shutters are metallic and are activated automatically during movement of the apparatus from the rack-out position to the service position and vice versa. The circuit-breaker compartment can be equipped with circuit breaker, or other units, like fused contactor, PT truck etc.


Cable compartment

The cable compartment contains the branch system for connection of the power cables to the lower contacts of the circuit-breaker. The height for cable connection is up to 700 mm for an easy cable connection work on site. The cable compartment of each outgoing feeder panel can be fitted with an earthing switch for cable earthing. An indicator on the front of the switchgear shows the position of the earthing switch. According to the project requirement, the cable compartment can be equipped with surge arrester, line PT, zero sequence current transformer etc.


Low voltage compartment

All the secondary instruments and cabling are housed in the low voltage compartment. For easy on site installation and secondary cable connections, a cable trunking is located on the top of the low voltage compartment.


Safety

Each compartment meets IP2X degree of protection and the external enclosure conforms with the requirement of IP4X. The metallic shutters are in front of the insulating bushings of the circuit breaker fixed contacts. When the circuit breaker is racked out, the shutter will be closed automatically to cover the bushing thus meeting the requirement of IP2X degree of protection and guarantee the highest level of safety and reliability both for the personnel and the installation.

The switchgear housing is fabricated by Al-Zn alloy coated sheet steel, which has high corrosion resistance, long service life time and is suitable for the harsh condition.

The low voltage compartment is completely segregated from the other high voltage compartments, thus increasing the reliability of the protection relays.

The busbars are insulated with RAYCHEM heat shrinkable materials having a very good insulation and cooling characteristics.

The JN15(17)-12 earthing switch is equipped with a fast closing mechanism and has full short-circuit making capability. The position of the earthing switch can be seen at the position indicator as well as through a viewing window made of explosion-proof glass at the front of the cable compartment.

The main earthing bus of the switchgear is made of a copper bar with a cross-section of 240mm2. After installation, the copper bar will be used to connect the main earthing bus of each switchgear unit. The earthing symbol is clearly shown at each earthing connection. The primary components and the truck are directly connected to the main earthing busbar.

The pressure relief plates are positioned on the top of the switchgear. The circuit breaker, the busbar and the cable compartment are each fitted with a flap positioned on the top of it. The pressure generated by the arc fault makes it open, allowing the high pressure gas to be released from the switchgear. Sealing gaskets at the front doors will prevent the exit of the hot gases so as to guarantee the operators safety.

Each switchgear unit is fitted with reliable interlocking mechanisms between the different functions to prevent hazards from incorrect operations either by not respecting the correct procedures or due to inadequate training of the personnel in charge of the installation. The interlocks therefore guarantee a high level of safety both for personnel as well as for the equipment. The details of the interlocks include:

- The circuit-breaker truck can only be moved from the test/isolated position into the service position or vice versa, with the circuit-breaker open.
- Closing of the circuit-breaker is only possible when the circuit breaker truck is in the exact test/isolated position or service position.
- The earthing switch can only be operated when the truck is in the test or the isolated position.
- The control wiring plug is locked when circuit breaker is in the service position. While in the test position, the control wiring plug can be removed or inserted.
- The circuit breaker truck can only be racked in from the test position into the service position with the earthing switch opened.
- The door of circuit breaker compartment can only be opened with the circuit breaker is in test/isolated position.
- The circuit breaker truck can only be moved from the test position into service position with the door of circuit breaker compartment closed and locked.
- The door of the cable compartment can only be opened with the earthing switch closed
- The earthing switch can only be opened when the cable compartment door is closed and locked Apart from the mechanical interlocking functions mentioned in above, the shutter can be fitted with padlock when the circuit breaker truck is in the test/isolated position to prevent non-professional personnel from the hazard of opening the shutter using brute force.



Fully tested

There are two kinds of switchgear tests, type test and factory test.

The SGC1 switchgear has undergone typed tests required by the applicable IEC and the GB standard.
a) Dielectric
b) Temperature rise
c) Main circuits resistance.
d) Making and breaking capacity of the apparatus.
e) Short-time and peak withstand current.
f) Mechanical endurance
g) Protection grade verification
h) Additional tests on auxiliary and control circuits



The factory tests of each switchgear unit are carried out in the factory before it is despatched to ensure the product fulfills the specific requirement of the related standards and specific projects.

a) Visual inspection and check.
b) Mechanical sequence operations.
c) Power frequency withstand voltage test on main circuit
d) Measurement of the resistance of the main circuits
e) Insulating tests on auxiliary and control circuits
f) Cabling connection check.



Key components

Circuit breaker

Modularization design is applied in both the mechanism and accessories of VX3 Vacuum Circuit Breaker, which is equipped with scroll spring mechanism and has better modularity and more compact structure. Such design provides large space for future upgrading as intelligent Circuit Breaker. Also it has the advantages of steadier movement, adjustable storage capacity, cam drive mechanism applied. Such compact structure can realize circuit breaker one-step installation and easy operation.

The VX1 circuit breaker uses the modular spring driving mechanism featuring of simple and fast installation and removal, therefore providing shorter overhaul duration, reduced outage losses and safe and reliable power delivery. The driving mechanism of the VX1 vacuum circuit-breaker adopts the modular design concept. The circuit-breaker is equipped with embedded poles with the vacuum interrupter being casted inside the epoxy pole. All the poles are mounted on the same metal frame ensuring the mechanical connection accuracy between the driving mechanism and the moving parts inside the embedded poles. The VX1 circuit-breakers are available in both fixed and withdrawable version.


Poles

The VX circuit-breaker uses vacuum interrupters embedded in epoxy resin poles. Embedding the interrupter in the epoxy resin makes the circuit-breaker poles particularly sturdy and protects the interrupter from impacts and other external influences.

Vacuum interrupter


Our VX vacuum circuit-breaker has used the vacuum interrupter produced by Beijing Orient Vacuum Electric Co., Ltd - the top-class manufacturer of vacuum interrupter in China, which provides the following benefits:

• Unique R-shaped contact with international patent:
- outstanding breaking capacity, high reliability
- low main circuit resistance which can effectively reduces temperature rise
- can fulfill customers requirement on 100% full capacity breaking
- Hybrid design, require no special shaping of the contacts to direct the arc, therefore, gives a higher dielectric strength and stronger mechanical strength, it will not deform through the entire service life.

• The special curvature shape design of the vacuum interrupter can lower the chance of cracking the embedded poles and lower the stress given to the vacuum interrupter by the epoxy poles.

• The advanced stainless steel hard-soldered process.
The stainless steel chamber lids are having very good tensile strength, ductility and impact resistance, which effectively relieves the stress generated by the epoxy poles after the casting process of the vacuum interrupter.

• Stable and high quality seal-brazing process gives extra-low leakage rate
The top class ceramic insulator manufactured in aluminum oxide, provides high sealing and high tensile strength (no lower than 130MPa).
On request, SGC1 switchgear can be fitted with a fuse-contactor combination or a load break switch.

Current transformer

The current transformers can be of the resin casted block or ring type and are used to supply measurement devices and protection instruments. They conform to the IEC 60044-1 and the GB 1208 Standards. Their dimensions are in accordance with the DIN 42600 Narrow Type Standard,

Key technical data:
Rated voltage: 12kV
Rated frequency: 50Hz, 60Hz
Rated secondary current: 5A, 1A
Rated primary current: 30~4000A;
The current ratio, class, burden and other parameters
can be choosen on customer request.

Voltage transformer

The voltage transformers are of the resin casted block type and are used to supply measurement and protection devices. They conform with the IEC 60044-2 and GB 1207 Standards. Their dimensions are in accordance with the DIN 42600 Narrow type Standard. They can be fitted with medium voltage protection fuses. They are available for fixed assembly or for installation on removable and withdrawable trucks.

Key technical data:

Rated voltage: 12kV;
Rated frequency: 50Hz, 60Hz
The voltage ratio, class, burden and other parameters can be choosen on customer request.


Current sensor/Voltage sensor (electronic transformers)

For digital substations the switchgear can be equipped with sensors for current and voltage measurement. The current sensor is based on Rogowski coil principle. The voltage sensor is basically a resistive (or capacitive) voltage divider.

The current and the voltage sensor are available as separate units or both functions combined within one module. Compared to conventional electromagnetic type instrument transformer, the current and voltage sensors have following advantages:

- Simple structure, high stability and reliability
- Without the ferromagnetic core, no saturation and ferroresonance phenomenon can occur.
- As the secondary output is a low voltage signal no danger can occur due to over voltage with secondary side open circuit as of the conventional current transformers or burnout on the secondary side of the voltage transformers due to overload;
- The sensors have wide dynamic range and high measurement precision. One current sensor covers a range from amps to several kilo amps, while, the overcurrent can reach to several ten thousands of amps without any risk of saturation.
- Easy to standardize, thus shortening the lead time.
- Due to the wide dynamic range, when primary load changes, there is no need for replacing the current sensors.
- The sensor output can be directly interfaced with the computer control system to realize intelligent multi-function control and protection systems for digital substations for smart power grids



Earthing switch

The incoming/outgoing feeder units can be fitted with the JN15(17)-12 type fast switching earthing switch for cable earthing. The same device can also be used to earth the busbar system in bus-tie and bus-riser units with PT. The earthing switch has both short-circuit making and shortime withstand capacity.

Key technical data



Control and protection component

A wide range of control, protection and metering components are available based on the project requirement.

Typical units

1. Incoming or outgoing feeder units



2. Incoming or outgoing feeder unit with top cable entry



3. Incoming or outgoing deeper feeder unit -top rear busbar entry



4. Bus-tie units



5. Metering units



6. Voltage measurement units



7. Withdrawable disconnector units



8. Load switch units



9. Incoming or outgoing unit -duct entry in cable compartment



10. Incoming or outgoing feeder unit - cable entry from the bottom



11. Incoming or outgoing deeper feeder bus-tie unit cable entry on the back



12. Incoming or outgoing bus-tie unit top entry directly into busbar



13. Fused vacuum contactor units



Configuration and installation

Distribution room planning

Normally, the operation and commissioning of the SGC1 switchgear is to be carried out from the front side of the switchgear panels. The installation of the primary power cables is normally carried out from the rear side of the panels, but can also be carried out from the front side. In consideration of the fire protection, maintenance and inspection requirements, the switch room layout is proposed according to the drawing below. This arrangement is suitable for both cable entries from bottom or from the top


Switchgear foundation requirements

The design and construction of the SGC1 foundations should follow relevant code of practice or specification for electrical equipment installations and erections, a prefabricated foundation frame is highly recommended.

The frame should by welded of channel steel and angle steel. It’s suggested to choose no.10 type channel steel profile. The extension of channel steel should keep the same dimension of switchgear frame.

Levelness should be checked before the foundation frame is installed. The deviation of levelness and flatness shall be less than 1mm per meter respectively. The total difference shall not be more than 2 mm. The top of the foundation frame shall be 5mm to 12mm higher than the floor level.


Friendly reminder:

The data and illustrations contained in this document are provided for information only. XuJi (Xiamen) Intelligent Switchgear Manufacturing Co., Ltd reserves the right to revise or change these data and illustrations at any time without further notice. Please contact us for the latest brochure.

Documents required when placing orders

The following technical documents should be provided by our customer together with the contract/purchase order:

• Single line diagram, main connection scheme no.(refer to section VI. Typical Units), rated voltage, rated current and rated short-circuit current;
• Key primary components configuration, basic technical data and requirements;
• Switch room layout and switchboard arrangements;
• Way of incoming and outgoing connections, as well as cable specification/busduct technical data;
• The technical requirements for control, measurement, protection and interlocking etc;
• Any special requirements for technical parameter and/or service condition exceeding or not within the SGC1 technical data as stated in this brochure.