Introduction

Following the development of power industry, the demand for compact switchgear equipment will be increasingly high. The using of compact switchgear equipment will reduce the occupancy of floor space and lower the civil construction cost. We can also minimize the amount of SF6 gas required contributing to the environmental protection. With our long years of experience in high voltage switchgear equipment design, and adopting the latest switching device deign philosophy, our company has developed a new generation type ZF48-126 (L) three-phase common enclosure compact Gas Insulated Switchgear. By arranging standard components like building blocks in a modular design concept, the products requires a minimum footprint (the width of compartment is only 0.8m) featuring advanced technology and high reliability.

Normal Operating Conditions

Installation : suitable for indoor and outdoor
Ambient temperature: -30 to +40℃ (-40 to +50℃ for special order)
Altitude: 1000m (no limitation for special order)
Air humidity: daily average≤95%, monthly average≤90% (25℃)
Wind speed : ≤34m/s (wind pressure lower than 700Pa)
Solar radiation intensity: ≤0.1w/cm2 (wind velocity of 0.5m/s)
Earthquake intensity: horizontal acceleration ≤0.4g, vertical acceleration ≤0.2g
Ice thickness: ≤10mm
Creepage distance: 25mm/kV (Grade II pollution grade), 31mm/kV (Grade IV pollution grade)
Environment without combustible and explosive danger, and corrosive atmosphere and severe vibration.

Standards and approvals

GIS conforms to the Chinese national standard GB7674-2008 Gas-Insulated Metal-Clad Switchgear for
Rated Voltages of 72.5kV and Above, and International Electrotechnical Commission Standard IEC
62271:2003 High-Voltage Switchgear and Controlgear Part 203: Gas-Insulated Metal-Clad Switchgear for
Rated Voltages above 52 kV and other applicable standards.

Main features of the product


1. Compact space saving design, minimum floorspace required, bay width only 0.8m
Carefully designed components using state of the art 3-D field electrical field calculations and advanced technologies lead to a very compact and reliable product. The width of a single bay shrinked to a world class value of 800mm and the footprint for a standard bay is only 2.90m2. Thanks to the compact design, the end user customer can save a lot of floor space and lower both civil construction and shipping costs.

2. Excellent interrupting performance
Using the latest generation of self blast principle and applying electrical field and gas flow simulations, excellent interrupting performance of the circuit breaker could be achieved. The good making and breaking capacity of the circuit breaker is ensured in the whole current range from low operating current (including line charging) to full short circuit current (including out of phase switching). New arc resistant nozzle materials substantially increase the electrical life of the circuit-breaker.


3. Modular design, suitable for various substation layouts
The product is divided into several functional modules, including Circuit breaker Module GCB, Combined disconnector/earthing switch module TPS, busbar module BUS etc. Each module has the same interface, allowing to assemble different substations layout in a building block like way accord to the required functionality.

4. High reliabilities, strong fog-flashover resistance
Due to the optimized electric field distribution of each insulation component the product meets the highest insulating requirements for 145kV voltage class with large margins, reaching a power frequency withstand voltage of 315kV and a lightning impulse withstand voltage of 750kV. The lower part of outlet SF6/air bushing adopts optimized shielding design to resolve the problem of easy occurrence of fog-flashover on bushing caused by the electric field concentration at the bottom of bushing due to miniaturization of product. Key insulating parts are supplied by famous multinational suppliers to ensure the high reliabilities of insulation.

5. Operating mechanism totally enclosed
The operating mechanisms are protected from atmospheric environment in enclosures. The enclosure of the circuit-breaker mechanism can be filled with dry nitrogen under slight overpressure to increase its reliability.

6. All-aluminum enclosure, low losses, light weight, simple foundation requirements, easy to transport, quick and easy on site erection and commissioning activities.

7. Intelligent secondary control and monitoring
The GIS is ready for the future, digital control and protection combined with state of the art current and voltage sensors allows the implementation of the latest digital substation technology. On request conventional secondary control and protection schemes are available.

ZF48-126 (L) Design features

ZF48-126 (L) type GIS switchgear is assembled from different standard functional modules, namely, circuit breaker GCB, Combined Diconnector/Earthing Switch TPS, potential transformer PT, current transformer CT, SF6/air bushing BSG and busbar BUS, etc. Every module uses a common enclosure for the three phases. All these modules have a common interface with the same dimensions, and thus can be combined according to the design and layout requirements of various substations. Due to the modular concept, maintenance is simplified and future retrofit or expansion of the substation becomes very easy. The high degree of flexibility obtained by the modular design makes it simple and easy to cover all customer requirements and substation layouts such as single/double-busbar configuration, direction of incoming power lines or cables, building dimensions, accessibility, quick trouble shooting etc.

1. Circuit breaker module GCB

A common enclosure holds the three poles of one circuit-breaker. The 3 poles of the the CB are mechanically interlinked and operated by one common spring drive operating mechanism. The circuit-breaker module has either three or four identical coupling flanges and all other modules can be directly connected to these flanges. Thus allowing a very compact substation design. A large substation equipped with ring busbar or one and a half breaker scheme is as easy to build as a small scale ring network substation.

The circuit breaker adopts the latest self blast arc extinguishing philosophy. A mechanical spring operating mechanism or an imported hydromechanical operating mechanism is available for the circuit-breaker. The circuit-breaker therefore requires very low maintenance.

By optimizing the electrical field through calculation and adopting in-breaker wiring for the double-busbar scheme, a simplified primary busbar layout has been achieved further reducing the required floorspace.

The internal parts of operating mechanism case for outdoor switchgear severely suffers from moisture when they are operating especially in southern and coastal areas. It has been a trouble for manufacturers and substations. Most of the manufacturers employ water-proof adhesive glue and sealant to seal the mechanism case. However, those methods are unsatisfactory in the real application.

0.01MPa nitrogen is the protection gas filled in the operating mechanism case, which helps to fully segregate the interior from external air. It provides a solution for the corrosion and pollution of operation mechanism caused by external environment, such as dust, humidity, corrosive gas and heavy rain. Hence the reliability and service life of products can be improved.



2. Combined disconnector/earthing switch module TPS

The combined disconnector/earthing switch design minimizes the requirement for space, and realizes three positions including 1) disconnector closed, earthing switch open; 2) disconnector open, earthing switch open; 3)disconnector open, earthing switch closed.

A motor operated actuator drives the combined disconnector/earthing switch. An adequate transmission converts the clockwise and anti clockwise rotations to the required straight reciprocating motion of contacts.

Interlocking is provided between the disconnector and earthing switch for safe operation.

When used as busbar disconnecting switch, the TPS can be connected to the busbar with a compensator to eliminate the mechanical stress due to tolerances and thermal expansion.

Fast disconnector can be chosen when functioned as feeder disconnecting to break the bus-transfer current.


3. Fast earthing switch module FES

The Fast earthing switch is equipped with a spring operating mechanism. The mechanism is charged by a motor, when the FES is activated the energy of the springs is released and the moving contacts close very fast providing full short circuit making capacity. The FES is especially suited as feeder earthing switch.

The fast earthing switch can be isolated from the earthed enclosure when required to facilitate adjustments and testing of protection relays, examine cables or location of cable failure.

4. Current (Voltage) transformer module CT (VT)

Induction type voltage and current transformers are used for measurement and protection. The instrument transformers adopts SF6 gas for primary insulation, therefore the insulating medium will not age provinding high reliability. The insulation of the voltage transformer is composed of SF6 gas and insulating foils.

The current transformer is usually connected to the circuit breaker, with 2~5 secondary windings. The secondary side of a voltage transformer can have two measurement windings and one open triangle winding used for earthing fault detecting .

On customers request electronic instrument transformers can be provided. Small volume, light weight, linear response, integrated self check and easy connection to digital protection are advantages of the sensors. Along with the development of digital substations electronic current (voltage) transformer will be used more and more.


SF6/air bushing module BSG

Outdoor bushings are used for connections to overhead lines and transformers. Both high strength porcelain bushings and composite material bushings with silicon rubber sheds are available based on customers choice.

We recommend composite bushings, composed of a supporting bushing wall made of glass fiber reinforced epoxy resin and vulcanized sheds made of silicon rubber. The composite bushing features explosion proof, cracking proof, high tensile strength, convenient for installation and transportation, antifouling, waterproof, pollution resistant etc.
We can also provide the connection parts for the oil and gas bushings of transformer according to project requirement.

6. Cable terminal module CSE

The GIS can be connected with various cables through cable plugs.

For the currently widely used XLPE (cross linked polyethylene insulated) cable, we can provide a full-dry type solid insulated cable plugs with short installation length.

The main component of plug-type cable terminal is the epoxy resin bushing, which is matched with the prefabricated cable terminal stress cone made of silicon rubber and provided by the cable terminal manufacturer. The advantage of plug-type cable terminal is that GIS installation can be totally separated from cable system installation, the cable terminal can be directly plugged out during cable testing and repairing, without opening the SF6 gas chamber of GIS.

7. Local control cubicle LCP

The equipment for secondary control, electrical interlocking, local operation, fault alarm, signaling and other functions is located in the LCP control cabinet.

Primary equipment is connected with local control cubicle through several multicore cables and plugs. All this cable assemblies are fully factory tested before delivery.

Position and warning indicators as well as buttons for local control are arranged on the front panel of the LCP. The interlocking can be unlocked by an individual key. Local/remote control is enabled through a keyswitch.

We designed the intelligent digital control and protection cabinet i-LCP according to the requirement of digital substations, the output format conforms to the standard in IEC 61850-9, this module performs continuous monitoring of the various function and status of all equipment, and provides these data online to the substation control.

Main technical data

Transportation, installation and commissioning

Transportation and installation of ZF48-126 (L) typed GIS is very convenient due to its light weight. We delivery the fully factory manufactured and tested bay and control cabinet as a whole unit and install them onsite, which furthermore enjoys the following advantages.

1. Short field installation time, simplified commissioning
2. Routine insulation test and partial discharge test are done in factory to avoid the damage of insulation for equipment.
3. Due to the bays small in size, light in weight, no special requirement for packaging and transportation.

In most cases, the equipment needs to be transported with filled nitrogen. But filled with slightly overpressure SF6 gas is also feasible.

After completing the erection at site, the bays are filled up with SF6-gas only until the gas-filling pressure is reached. Each gas compartment is fitted with an independent self-sealing valve, which ensures SF6 gas of GIS won’t leak while connecting or disconnecting with the gas-charging device.

Since GIS won’t be affected by external environment, such as dust, humidity, etc., the maintenance is pretty low, to some extent, maintenance-free.

Regular check can be done in front of the equipments, which keeps substation running. SF6 gas and hydraulic oil condition can be evaluated through routine sample-checking. The regular check includes checking transmission device, auxiliary switches, gas pressure gauge etc.

Circuit breaker should be checked and repaired after 6,000 times mechanical operation, while the interrupter need to be overhauled after breaking 20 times of rated short-circuit current up to 40kA. However, the actual operation experience shows that above maintenance standards are far surpass the performance requirement.

Project application

GIS equipment for Jiangsu Reshine New Material Engineering Company 110kV S/S

Substation examples

Layout and single line diagram for H-type connection
H-type connection performs reliable and flexible, which uses fewer components and enjoys low construction cost. Therefore, it is widely employed in industrial users, area power supply system and factory substation with two sets power supply.

For the concern of retrofit, it’s required that customer inform manufacturer when ordering. H-type connection can be extended to sectionalized single-busbar configuration.


Layout and single line diagram of sectionalized single-busbar configuration

Dual power is supplied for sectionalized single-busbar configuration. The maintenance for distribution lines can be carried out in section. It narrows the outage range. Once one section of bus fault occurs, circuit breaker automatically disconnects the faulted section to guarantee continuous power supply for the normal part of busbar and important end-users. It is mainly applied for power plant with small capacity and customers who have demanding requirement of energy quality.

Layout and single line diagram of sectionalized double-busbar configuration

Double busbar arrangement makes sure the power supply reliability and continuity during the routine maintenance and repair of buses. The substation used this arrangement can be extended or adopted at any time and easy for testing. It also suitable for the substation configuration which has many outgoing lines or several bus power supplies, at the same time requires fast power restoration after bus faults occurred. At present, this kind of arrangement is widely employed in high-capacity power stations and substations.



Purchasing procedures


Customer provides us a technical specification according to their project requirements. The general arrangement drawing of the GIS will be prepared on the basis of customer’s technical requirements. When our design proposal is agreed and confirmed by our customer, the drawings will be used as the basis for cost calculations and final design.

2. When the contract is effective, we shall carry out detailed project design, and provide our customers with necessary technical documentations, including primary wiring diagrams, layout drawing, foundation requirements drawing, sectional drawing and secondary schematic drawings, etc. We shall work closely with our customers to ensure a smooth and successful project execution.

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