High-voltage distribution cabinet
Electrical products for power system generation
High-voltage distribution cabinets refer to electrical products used in power systems for generation, transmission, distribution, energy conversion, and consumption, performing functions such as switching, control, or protection. These products operate at voltage levels ranging from 3.6kV to 550kV and mainly include high-voltage circuit breakers, high-voltage isolators and earthing switches, high-voltage load switches, high-voltage automatic reclosing and sectioning switches, high-voltage operating mechanisms, high-voltage explosion-proof distribution equipment, and high-voltage switchgear cabinets. The high-voltage switch manufacturing industry is an essential part of the power transmission and transformation equipment manufacturing industry, holding a very significant position in the entire power industry.
Features
The distribution box features overhead incoming and outgoing lines, cable incoming and outgoing lines, and bus interconnection functions.
Composition
The distribution panel should meet the requirements of GB3906-1991 "3-35 kV AC Metal-Enclosed Switchgear" standard, consisting of two main parts: the cabinet and the circuit breaker. The cabinet is composed of the shell, electrical components (including insulating components), various mechanisms, secondary terminals, and wiring, etc.
Cabinet Material
1) Cold-rolled steel plates or angle iron (for welding cabinets)
2) Aluminum-zinc coated steel sheet or galvanized steel sheet (for cabinet assembly)
3) Stainless Steel Sheets (Non-magnetic)
4) Aluminum Sheet (Non-magnetic)
Functional Unit
1) Main busbar room (the general arrangement of main busbars is in two structures: the "crane" shape or the "1" shape)
2) Circuit Breaker Room
3) Cable Room
4) Relays and Control Panels
5) Busbar Compartment on Top of the Container
6) Secondary Terminal Compartment
Interior components
1. Common one-time electrical components (main circuit equipment) used inside the cabinet include the following equipment:
Current Transformer, abbreviated as CT [e.g., LZZBJ9-10]
Voltage Transformer, abbreviated as PT [e.g., JDZJ-10]
Zero-sequence Transformer
Circuit Breaker Cabinet
Grounding Switch [e.g., JN15-12]
Surge Protectors (Capacitive and Resistive Absorbers) [e.g., Single-phase type HY5WS; TBP, JBP Combination type]
Isolation Switches [e.g., GN19-12, GN30-12, GN25-12]
High-voltage Circuit Breakers [such as: Low-oil Type (S), Vacuum Type (Z), SF6 Type (L)]
High-voltage Contactor [e.g., JCZ3-10D/400A Model]
High-Voltage Fuses [e.g., RN2-12, XRNP-12, RN1-12]
Transformers [e.g., SC(L) Series Dry Transformers, S Series Oil Transformers]
High-voltage Live Display [DXN-Q Type, DXN-T Type]
Insulating Components [e.g., wall penetration sleeves, terminal boxes, insulators, insulating shrink (cold shrink) sleeves]
Main busbar and branch busbar
High-voltage Reactors [such as series type: CKSC and starting motor type: QKSG]
Load Break Switch [e.g., FN26-12(L), FN16-12(Z)]
High-voltage single-phase capacitors in parallel [such as: BFF12-30-1] etc.
2. Major secondary components commonly used inside cabinets (also known as secondary equipment or auxiliary equipment, referring to low-voltage equipment that monitors, controls, measures, adjusts, and protects primary equipment), including the following equipment:
Relays, electricity meters, ammeters, voltmeters, power meters, power factor meters, frequency meters, fuses, circuit breakers, changeover switches, signal lights, resistors, buttons, microcomputer integrated protection devices, etc.
Categories
Breaker by the piece
Breakers are categorized by installation type into withdrawable (handcart type) and fixed type.
(1) Withdrawable or Handcart Type (indicated by Y): This signifies that the main electrical components inside the cabinet (such as circuit breakers) are mounted on a removable handcart. Due to the excellent interchangeability of the handcart cabinet, it significantly enhances the reliability of power supply. Common handcart types include isolation handcart, metering handcart, circuit breaker handcart, PT handcart, capacitor handcart, and transformer handcart, etc., such as KYN28A-12.
(2) Fixed-Type (represented by G): Indicates that all electrical components inside the cabinet (such as circuit breakers or load switches, etc.) are installed in a fixed-type manner. Fixed-type switch cabinets are relatively simple and cost-effective, such as XGN2-10, GG-1A, etc.
By Location
Indoor and outdoor, categorized by installation location
(1) For indoor use (denoted as N); indicating that it can only be installed and used indoors, such as: switch cabinets like KYN28A-12;
(2) Outdoor Use (denoted as W); indicates that it can be installed and used outdoors, e.g., XLW type switch cabinets.
As per cabinet structure
Cabinet structures can be divided into four main categories: metal-enclosed armored switch cabinets, metal-enclosed compartment switch cabinets, metal-enclosed box switch cabinets, and open-type switch cabinets.
Metal-enclosed armored switchgear (represented by the letter K) mainly consists of components such as circuit breakers, transformers, busbars, etc., which are installed in metal-enclosed switchgear in compartments separated by grounded metal partitions. For example, the KYN28A-12 type high-voltage switchgear.
(2) Metal-enclosed switchgear with separate compartments (represented by the letter J) is similar to armored metal-enclosed switchgear, as its main electrical components are also housed in individual compartments. However, it features one or more non-metallic partitions that meet certain protection levels. For example, the JYN2-12 type high-voltage switchgear.
(3) Metal-enclosed switchgear cabinets (represented by the letter X) are switchgear devices with a metal-enclosed cabinet shell. For example, the XGN2-12 type high-voltage switchgear cabinet.
(4) Open-type switch cabinets, no protection grade requirements; the casing has part of it open for switch equipment. Such as the GG-1A(F) type high-voltage switch cabinet [2].
Five Precautions
1. The vacuum circuit breaker car within the high-voltage distribution cabinet fails to reach the operating position after closing at the test location. (Prevents incorrect opening and closing of circuit breakers)
2. When the grounding switch in the high-voltage distribution cabinet is in the closed position, the push-button circuit breaker cannot be closed. (Prevents closing with the grounding wire connected)
3. During the closing operation of the vacuum circuit breaker within the high-voltage distribution cabinet, the cabinet rear door is locked with a mechanical device on the grounding blade to prevent it from being accidentally opened into the live compartment.
4. The vacuum circuit breaker within the high-voltage distribution cabinet fails to close during operation, and the grounding switch cannot be engaged. (Prevents live-line grounding)
5. The vacuum circuit breaker within the high-voltage distribution cabinet is unable to withdraw from the working position of the trolley circuit breaker during operation and closing. (To prevent opening the switch with load)
Relevant standards
SJ/T 31401-1994 | Requirements and Inspection and Evaluation Methods for High-Voltage Switchgear Cabinets
DL/T 791-2001 | Guidelines for Selection of Indoor AC Filled Switchgear
DL 404-1991 | Technical Conditions for Ordering Indoor High-Voltage Switchgear
DL/T 404-1997 | Technical Conditions for Ordering Indoor AC High-Voltage Switchgear
DL/T 539-1993 | Indoor AC High-Voltage Switchgear and Components - Technical Conditions for Dew Condensation and Pollution Tests
TB/T 2010-1987 | 27.5kV AC Electrified Railway Switchgear Technical Conditions
DL/T 404-2005 | Indoor AC High-Voltage Switchgear Ordering Technical Specifications [1]
Product Model and Its Meaning
Application
1. KYN-10 Indoor AC Metal-clad Draw-out Switchgear (hereinafter referred to as the handcart cabinet) is suitable for indoor complete power distribution systems with a single-phase bus or single-phase bus section system, operating at a rated voltage of 3-10KV and a frequency of 50Hz, with the neutral point not grounded. It is used by various types of power plants, substation, and industrial and mining enterprises for accepting and distributing network power, as well as for controlling, protecting, and monitoring the circuit.
2. The KYN-(F-C) type indoor armored double-layer moving open AC metal-enclosed switchgear system is a complete indoor switchgear for 3.6~12kV three-phase AC 50Hz, single busbar and single busbar section systems. It is primarily used as a high-voltage distribution device in power plants, sub-stations, metallurgy, papermaking, petrochemical, textile, and industrial and mining enterprises. It is suitable for the control and protection of motors, transformers, and capacitors.
3. The KYN-12/1250-31.5 indoor armored withdrawable AC metal-enclosed switchgear is a switch, which is a complete power distribution system for 3.6-12KV three-phase AC 50Hz single bus and single bus section systems. It is mainly used for power plants, transmission of electricity from small and medium-sized generators, distribution in industrial and mining enterprises, and receiving and transmitting power in secondary substations of the electric power system, as well as for starting large high-voltage motors. It is used for control, protection, and monitoring purposes. This switchgear meets the requirements of IEC298, GB3906, and other standards.
Structural Features
1. The KYN indoor AC metal-enclosed switchgear (hereinafter referred to as the switch cabinet) is designed and manufactured in accordance with the "3-35KV AC Metal-Enclosed Switchgear" standard and IEC298 "AC Metal-Enclosed Switchgear and Control Equipment" standard. It also meets the requirements of the Ministry of Water Resources for high-voltage switchgear to have the "Five Preventive" functions.
2. The KYN-(F-C) indoor armored double-circuit moving open AC metal-enclosed switchgear is a component of the KYN-(F-C) indoor armored double-circuit moving open AC metal-enclosed switchgear. It can be used in conjunction with the KYN-(F-C) indoor armored double-circuit moving open AC metal-enclosed switchgear to form a modular power distribution unit. This switch cabinet features double-layer armor on one side, which can accommodate two F-C mobile switchboards, equivalent to the functionality of two single-layer cabinets, while occupying approximately the same footprint as a single-layer cabinet. This saves a significant amount of space and equipment investment for the user. This product utilizes vacuum contactors specifically designed for double-layer cabinet structures, featuring simple design, compact size, aesthetic appearance, high insulation level, long lifespan, and comes with both electrical hold and mechanical locking mechanisms.
3. KYN-12/1250-31.5 Indoor Armored Withdrawable AC Metal Enclosed Switchgear, featuring an armored cabinet structure with a central arrangement, divided into the circuit breaker room, main busbar room, cable room, and relay instrument room. To enable the cabinet to withstand internal fault arcs, exhaust ducts and pressure relief windows are provided in all functional compartments except the relay room, with the primary contacts being tied-type round contacts.
Switches can be high-redundant as per customer requirements, featuring a front-maintenance structure for wall mounting or back-to-back installation. The switchgear is equipped with a safe and reliable interlock device, fully meeting the "Five Preventive" locking requirements.
a, The circuit breaker's push-pull handle fails to close during the pushing or pulling process.
b, The circuit breaker's handcart can only be operated for closing and opening when it is in the test position or working position, and the handcart cannot be pulled out from the working position when the circuit breaker is closed.
c. The circuit breaker's handle can only be moved from the test position to the working position when the earthing switch is in the open position; the earthing switch can only be operated to open and close when the circuit breaker's handle is in the test position or outside the cabinet.
d, The rear door cannot be opened when the grounding switch is in the open position.
e, When the handcart is in the working position, the secondary plug is locked and cannot be removed.
The base frame of the circuit breaker room, on both sides of the fixed guide rails for the handcart movement, also features retractable extension guide rails on both sides for easy observation and inspection of the circuit breakers. After the circuit breaker is disconnected, the two extension guide rails can be pulled out of the cabinet, allowing the handcart to be directly moved from inside the cabinet to the extended guide rails outside.
Please include some high-voltage cabinets that are available on the market:
① GR Series:
Usage
The GRC1 type high-voltage distribution cabinet is used in 3~10kV sub-stations to improve the power factor of the power grid. This series of cabinets consists of capacitor cabinets, transformer cabinets, measurement and discharge cabinets.
Solution Categories
The GRC1 model is the standard type, consisting of a capacitor cabinet and a transformer cabinet. The capacitor cabinet comes in four configurations, while the transformer cabinet is available in three options.
2. The GRC1C model is a transverse differential protection type, meaning that when a capacitor in the cabinet trips, the main circuit breaker is tripped by the current transformer connected in a transverse differential circuit. This model also has four schemes.
3. The GRC1Y model is an inductive reactor type, i.e., a capacitor cabinet equipped with a series inductive reactor for harmonic suppression.
Structure
The cabinet is made of angle steel and thin steel plates, bent and welded into three layers. The bottom layer houses the oil trough plate, measurement and discharge cabinets. The voltage transformers are placed in the middle layer, while reactors are installed on the bottom layer. The front is a steel plate door, which can accommodate instruments, switches, and signal lights.
② GGX2 Series:
Usage
GGX2C10 High-Voltage Vacuum Circuit Breaker Switchgear is suitable for three-phase AC power grids with rated voltages of 3~10kV and a frequency of 50Hz. It serves as a complete power distribution unit for accepting and distributing electrical energy, as well as for controlling, monitoring, and protecting the circuit.
Structural Features
This distribution cabinet features a metal-enclosed box-type shell, with all live components enclosed within. They are functionally divided into busbar room, circuit breaker room, cable room, and the instrument box is a separate structure mounted on the cabinet. The vacuum circuit breakers and electromagnetic or spring-operated mechanisms form an integrated car-type structure, which is secured in place with bolts after being pushed into the cabinet. There are 24 main wiring schemes.
③GGX2 Series:
Application
The GSGC1A type double busbar high-voltage switchgear is suitable for regional sub-stations, large-scale industrial and mining enterprise sub-stations, and electrical equipment testing stations with voltages of 3, 6, 10kV, and a 50Hz AC double busbar system. It can also be used in single busbar systems with bypass busbars for receiving and distributing electrical power.
Structure
The cabinet system is constructed by welding thin steel plates and angle steel, the base is made of welded channel steel, the front features a single-leaf protective grille door, the rear has a double-leaf protective grille door, and the busbars are exposed on top.
The cabinet is divided into two compartments, the front compartment equipped with a spare (starting) busbar isolator switch, circuit isolator switches, and cable heads, etc., with a spare (starting) busbar installed at the top. The rear compartment houses the main (working) busbar isolator switch, oil circuit breakers, and a main (working) busbar isolator switch at the top. Current transformers can be installed between the compartments below. The operating mechanisms for the oil circuit breakers and isolator switches are mounted on the front of the cabinet. A single-leaf steel door is located on the left rear of the cabinet, inside which is the relay room. Thin steel plates separate the compartments and primary from secondary electrical equipment. Secondary electrical equipment can be repaired without interrupting power to the primary equipment.
To prevent operator errors, the cabinet is equipped with a programmed electrical interlock system.
Live Display Unit
I. Analysis of Issues with High-Voltage Distribution Cabinets
(1) The function of the high-voltage distribution cabinet preventing accidental entry into the live compartment causes the opening and closing of the cabinet door to be interlocked with the grounding switch. This means that the cabinet door can only be opened after the grounding switch is closed. This incident has exposed the imperfect issue of the mechanical interlock device of the "Five Preventions" in the old model high-voltage switch cabinets.
(2) The issue of voltage verification for high-voltage distribution cabinets has been a long-standing concern in electrical safety production. The currently promoted fully enclosed "Five Preventive Measures" switchgear with mechanical "Five Preventive Measures" locking devices fails to meet the safety regulation requirement of "verify voltage first, then connect the grounding wire." This is because during the execution of power shutdown work, it is necessary to confirm that the equipment is voltage-free before closing the grounding switch. However, in the fully enclosed state, the high-voltage switchgear cannot be verified for voltage using a portable high-voltage tester in accordance with normal operating procedures. Consequently, there has been a method of forcibly unlocking and opening the cabinet door to verify voltage.
(3) The high-voltage live display units on the distribution panels extensively utilize neon lamps as display elements. After long-term operation, it has been found that there is a high rate of failure and significant damage to the neon bulbs. To address this defect, an on/off switch for the neon lamps has been installed on the live display units. Normally, this switch is in the off position, temporarily deactivating the entire high-voltage live display unit. This approach, however, eliminates the function of the live display unit as a monitor for the live status of the line side.
(4) Neon lights have low brightness, especially in bright environments where their brightness is washed out, resulting in poor visibility.
(5) Vintage high-voltage live display units equipped with mandatory electrical interlock, featuring a simplistic interlock principle. It merely rectifies the signals from A, B, and C phase sensors using half-wave rectification and then combines them directly to control the interlock circuit. This method, however, can lead to accidents where the unit fails to reliably interlock and the live fuse is accidentally closed to the ground, due to voltage fluctuations in the interlock control during abnormal conditions like single-phase grounding or phase loss.
(6) Neon lamp-type high-voltage live indicator devices installed typically have a plastic housing and are mounted within the high-voltage equipment spacing. In the event of an internal short circuit arc in the switchgear during operation, the high-temperature arc may melt the device's plastic housing, risking injury to operating or maintenance personnel.
II. Solutions to Existing Issues
Given the numerous issues with the outdated high-voltage live display devices, there is an objective need for a new type of live display device that is highly reliable, long-lasting, maintenance-free, with clear and prominent displays, and capable of addressing the shortcomings of the old high-voltage live display devices. The Beijing Power Supply Bureau has successfully developed a new high-voltage live display verification device, which, when used with the CG series sensors, can reflect whether high-voltage equipment is running at voltage and has electrical interlock functions through live display and on-site verification. This device solves many problems associated with neon lamp live display devices, with its dual display consisting of a liquid crystal monitor and a long-life flash verification plug, suitable for various light conditions and highly visible. A dedicated verification plug provides a unique pull-out independent verification function, enhancing the device's reliability as a verification basis. The device employs phase-detection digital superimposed interlock control technology, ensuring that the interlock voltage remains unchanged and the system operates stably during abnormal conditions such as phase shortages. The mandatory electrical interlock function can reliably interlock grounding switches (cabinet doors). The application of the new high-voltage live display verification device can effectively prevent accidents caused by entering live intervals or connecting grounding switches, etc., which can lead to personal and equipment injuries.
Safety is the foundation of power generation, and prevention is the key to ensuring safe production. In the current safety and production of electricity, electric shock accidents and operational errors are still the two major factors threatening safe production. Continuously improving and refining technical measures to prevent electric shock accidents and operational errors is the goal that every employee in the power industry should strive to achieve.
