High-voltage distribution cabinet
Electrical products for power system generation
High-voltage distribution panels refer to electrical products used in power systems for generation, transmission, distribution, power conversion, and consumption, which serve functions such as switching, control, or protection. These products operate at voltage levels ranging from 3.6kV to 550kV and primarily include high-voltage circuit breakers, disconnecting and earthing switches, load switches, automatic reclosing and sectioning devices, operating mechanisms, explosion-proof distribution devices, and switchgear cabinets. The high-voltage switch manufacturing industry is a crucial component of the power transmission and transformation equipment manufacturing sector, holding a very important position within the entire power industry.
Feature
The distribution cabinet features overhead incoming and outgoing lines, cable incoming and outgoing lines, and bus connection functions.
Composition
The distribution panel should meet the requirements of GB3906-1991 "3-35 kV AC Metal-Enclosed Switchgear," consisting of two main parts: the cabinet and the circuit breaker. The cabinet is composed of the shell, electrical components (including insulating parts), various mechanisms, secondary terminals, and connections.
Cabinet Material
1) Cold-rolled steel plates or angles (for welding cabinets)
2) Aluminum-zinc coated steel or galvanized steel plate (for cabinet assembly)
3) Stainless Steel Sheets (Non-magnetic)
4) Aluminum Plate (Non-magnetic)
Function Unit
1) Main busbar room (the general busbar arrangement is in the shape of a "crane" or "1" structure)
2) Circuit Breaker Room
3) Cable Room
4) Relays and Control Panels
5) Busbar Compartment on Top of the Container
6) Secondary Terminal Compartment
Cabinet 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 Current Transformer
Circuit Breaker Cabinet
Grounding Switch [e.g., JN15-12]
Surge Arrester (Capacitive Reactor Absorber) [e.g., Single-phase type HY5WS; TBP, JBP Combination Type]
Isolation Switch [e.g., GN19-12, GN30-12, GN25-12]
High-voltage Circuit Breakers [such as: Oil-Reduced 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-Type Transformers, S Series Oil-Type Transformers]
High-voltage Live Display [DXN-Q model, DXN-T model]
Insulating Components [such as: wall penetration sleeves, terminal boxes, insulators, insulated heat shrink (cold shrink) sleeves]
Main busbar and branch busbar
High-voltage reactors [such as series type: CKSC and starting motor type: QKSG]
Load Switches [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 for monitoring, controlling, measuring, adjusting, and protecting 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
Molded Case Circuit Breaker
Circuit breakers are categorized by installation type into withdrawable (handcart-type) and fixed.
(1) Withdrawable or Handcart Type (indicated by Y): This indicates 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 can significantly enhance 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 fixed type installations. Fixed type switch cabinets are relatively simple and economical, such as XGN2-10, GG-1A, etc.
By Location
Indoor and outdoor, categorized by installation location
(1) For indoor use (denoted as N); indicates that it can only be installed and used indoors, such as: switch cabinets like KYN28A-12;
(2) For outdoor use (indicated by 'W'); denotes that the product can be installed and used outdoors, such as: XLW switch cabinets.
As per cabinet structure
Switchgear cabinets can be divided into four main categories: metal-enclosed armored switchgear, metal-enclosed partitioned switchgear, metal-enclosed box-type switchgear, and open-type switchgear.
Metal-enclosed armored switch cabinets (represented by letter K) mainly consist of components such as circuit breakers, transformers, busbars, etc., which are installed in metal-enclosed switchgear units separated by grounded metal partitions. For example, the KYN28A-12 type high-voltage switch cabinet.
(2) The Metal-Enclosed Modular Switchgear (represented by the letter J) is similar to armored metal-enclosed switchgear, with its main electrical components also housed in separate 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 equipment with a metal-enclosed cabinet shell. For example, the XGN2-12 high-voltage switchgear cabinet.
(4) Open-type switch cabinets, without specific protection grade requirements, featuring partially open switchgear enclosures. Such as the GG-1A(F) type high-voltage switchgear [2].
Five Precautions
1. The vacuum circuit breaker carriage within the high-voltage distribution cabinet fails to reach the working 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 drawer-type 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 mechanically locked with the grounding blade to prevent unauthorized entry into the live compartment.
4. The vacuum circuit breaker within the high-voltage distribution cabinet fails to close when in operation, and the grounding switch cannot be engaged. (To prevent live-line grounding)
5. The vacuum circuit breaker within the high-voltage distribution cabinet cannot be withdrawn from the trolley circuit breaker's operating position during the closing and operation phase. (To prevent opening the switch with load)
Relevant Standards
SJ/T 31401-1994 | Requirements and Inspection and Evaluation Methods for Complete High-Voltage Switchgear
DL/T 791-2001 | Guidelines for Selection of Indoor AC Air-Insulated 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 and Contamination Tests
TB/T 2010-1987 | 27.5kV AC Electrified Railway Switchgear Technical Conditions
DL/T 404-2005 | Indoor AC High-Voltage Switchgear Ordering Technical Conditions [1]
Product Model and Its Meaning
Usage
1. KYN-10 Indoor AC Metal Armored Withdrawable Switchgear (hereinafter referred to as the handcart cabinet) is suitable for indoor complete power distribution systems with a single-phase AC 50Hz rated voltage of 3-10KV, where the neutral point is not grounded, and for single-phase and segmented single-phase systems. It is used by various types of power plants, substation, and industrial and mining enterprises for receiving and distributing network power, as well as for circuit control, protection, and monitoring.
2. The KYN-(F-C) type indoor armored double-layer mobile open switchgear for AC 3.6~12kV three-phase 50Hz single busbar and single busbar section systems is a complete indoor switchgear set. 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 controlling and protecting motors, transformers, and capacitors.
3. The KYN-12/1250-31.5 indoor armored withdrawable AC metal-enclosed switchgear is referred to as 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 electricity in secondary substation of the power industry system, as well as starting large high-voltage motors, etc. It is used for control, protection, and monitoring. 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 handcart type cabinet) is designed and manufactured in accordance with the standard "3-35KV AC metal-enclosed switchgear" and the IEC298 standard for "AC metal-enclosed switchgear and control equipment," while also meeting the requirements of the Ministry of Water Resources for high-voltage switchgear to have "five preventive" functions.
2. The KYN-(F-C) indoor armored double-circuit switchgear is a component of the KYN-(F-C) indoor armored double-circuit switchgear, which can be used in conjunction with the KYN-(F-C) indoor armored double-circuit switchgear to form a modular distribution unit. This switch cabinet is a double-armed F-C cabinet, with one cabinet capable of housing two F-C switchboards, equivalent to the functionality of two single-layer cabinets, while occupying approximately the same footprint as a single-layer cabinet. It saves a significant amount of floor space and equipment investment for the user. This product features a vacuum contactor specifically designed for double-circuit cabinets, offering simple structure, compact size, attractive appearance, high insulation level, and long lifespan. It comes with both electrical retention 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 breaker room, main busbar room, cable room, and relay instrument room. To enable the cabinet to withstand internal fault arcs, exhaust channels and pressure relief windows are provided in all functional compartments except the relay room. The primary contacts are bundled round terminals.
The switchgear can be customized for high reserve, featuring a front maintenance structure for wall mounting or back-to-back installation. The switchgear is equipped with a safe and reliable interlock system, fully meeting the "five prevention" locking requirements.
The circuit breaker switch cannot be closed during the process of pushing or pulling out.
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 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 for opening and closing when the circuit breaker handle is in the test position or outside the cabinet.
d, The back 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 is equipped with fixed guide rails on both sides for the movement of the handcart. To facilitate observation and inspection of the circuit breakers, extendable guide rails that can be pulled out are specifically set up on both sides of the fixed guide rails. After the circuit breaker is disengaged, the two extendable guide rails can be pulled outside the cabinet, allowing the handcart to be directly moved from inside the cabinet to the extended guide rails outside.
Please attach some high-pressure cabinets available on the market.
GR Series:
Application
The GRC1 type high-voltage distribution cabinet is used in 3~10kV transformer stations to improve the power factor of the power grid. This series of cabinets consists of a capacitor cabinet, a transformer cabinet, and a measurement and discharge cabinet.
Solution Categories
1. The GRC1 model is the standard type, consisting of a capacitor cabinet and a transformer cabinet. The capacitor cabinet is available in four configurations, while the transformer cabinet comes in three options.
2. The GRC1C model is a horizontal differential protection type, meaning that when a capacitor inside the cabinet trips, the main circuit breaker is tripped by the current transformers connected in a horizontal differential circuit. This model also comes in four configurations.
3. The GRC1Y model is a reactor type for harmonic suppression, which is a capacitor cabinet equipped with a series reactor.
Structure
The cabinet is made by bending and welding angle steel and thin steel plates, arranged in three layers. The bottom layer features an oil trough panel and a measurement and discharge cabinet. The voltage transformer is located in the middle layer, while the reactor is installed at the bottom. The front is a steel plate door, which can accommodate instruments, switches, and signal lights.
② GGX2 Series:
Application
The GGX2C10 high-voltage vacuum circuit breaker cabinet is suitable for three-phase AC power grids with rated voltages of 3~10kV and a frequency of 50Hz. It serves as a complete distribution system for receiving 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; vacuum circuit breakers and electromagnetic or spring-operated mechanisms are an integrated car-type structure, which are fixed inside the cabinet with bolts. There are 24 main wiring schemes.
③ GGX2 Series:
Usage
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 test stations with voltages of 3, 6, and 10kV, under an AC 50Hz double busbar system. It can also be used in power supply systems with a single busbar and a bypass busbar for receiving and distributing electrical energy.
Structure
The cabinet is constructed from thin steel plates and angle iron welded together, with the base made of channel steel welding. The front features a single-panel protective mesh door, while the rear has a double-panel protective mesh door. The busbars on top are exposed.
The cabinet is divided into two rooms: the front room is equipped with a standby (starting) busbar isolator switch, circuit isolator switches, cable heads, etc., and a standby (starting) busbar is installed at the top of the front room. The rear room is fitted with a main (operational) busbar isolator switch, an oil circuit breaker, and a main (operational) busbar isolator switch at the top. A current transformer can be installed below the two rooms. The operating mechanisms for the oil circuit breaker and isolator switches are located on the front of the cabinet. A single-leaf steel door is on the left rear side of the cabinet, leading to the relay room. Thin steel plates separate the rooms and primary from secondary electrical equipment. Maintenance of secondary electrical equipment can be performed without interrupting power to the primary equipment.
To prevent accidental operation by staff, the cabinet is equipped with a programmed electrical interlock device.
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 live compartments establishes a locking relationship between the opening and closing of the cabinet door and the grounding switch. That is, the door of the switchgear can only be opened after the grounding switch is closed. This incident has exposed the imperfect issues with the mechanical locking device of the "Five Preventions" on the old model high-voltage switchgear.
(2) The issue of high-voltage distribution cabinet voltage verification has been a long-standing problem in power safety production. The currently promoted fully enclosed "five-protection" switchgear with mechanical "five-protection" locking devices cannot meet the requirements of safety regulations, which stipulate "verify voltage first, then connect the grounding wire." This is because, during the execution of power-off work, it is necessary to verify that the equipment is voltage-free before closing the grounding switch. However, due to the fully enclosed state of the high-voltage switchgear, it is impossible to verify the voltage of the equipment using a portable high-voltage voltage tester according to normal operating procedures. Consequently, there has been a method of forcibly unlocking and opening the switchgear door to verify voltage.
(3) Extensive use of neon lamps as display elements in high-voltage, live circuit indicator devices on distribution panels has resulted in a high failure rate and significant neon bulb damage after long-term operation. To address this缺陷, a neon lamp on/off switch has been installed on the live circuit indicator devices. The switch is typically kept in the off position, temporarily deactivating the entire high-voltage live circuit indicator device. This approach, however, renders the indicator device ineffective for monitoring whether the circuit side is live or not.
(4) Neon lights have low brightness, especially in bright environments where the brightness is washed out, resulting in poor visibility.
(5) Outdated high-voltage, energized display units with mandatory electrical interlock, featuring overly simplistic interlock principles. They merely rectify the signals output by the A, B, and C phase sensors with half-wave rectification and then directly composite them to control the interlock circuit. In the event of abnormal conditions such as single-phase grounding or phase loss in the system, the drift in the interlock control voltage can lead to unreliable interlock, potentially causing accidents where energized switches are closed to ground.
(6) Neon lamp-type high-voltage power-on indicators installed generally have plastic casings and are mounted within high-voltage equipment compartments. In the event of an internal short circuit arc in the switchgear during operation, the high-temperature arc may melt the plastic casing of the device, potentially harming operating or maintenance personnel.
Section 2: Solutions to Existing Issues
In light of 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 display, and capable of addressing the deficiencies of the old high-voltage live display devices. The Beijing Power Supply Bureau has successfully developed a new high-voltage live display and testing device that, when used with CG series sensors, reflects the presence of operating voltage in high-voltage equipment and provides electrical interlock functionality through live display and on-site testing. This device resolves many issues with neon lamp-style live display devices, featuring a dual display with a liquid crystal monitor and a long-life flash test plug, which is suitable for various lighting conditions and is highly visible. A dedicated test plug is designed to provide a unique removable independent testing function, enhancing the device's reliability as a testing basis. The device employs phase-detection digital superimposed interlock control technology, ensuring that the interlock voltage remains unchanged during abnormal operation such as phase shortages, thereby maintaining stable operation. The mandatory electrical interlock function can reliably interlock ground switches (cabinet doors). The application of the new high-voltage live display and testing device can effectively prevent accidents caused by human error, such as entering live compartments or closing ground switches, 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 efforts to ensure safe production in the power industry, accidents caused by electric shock to personnel and maloperation remain the two major threats. Continuously improving and refining technical measures to prevent electric shock accidents to personnel and maloperation accidents is the goal that each of us in the power industry should strive to research.
