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Medium-voltage Armoire électrique assemblée serves as vital electrical switchgear for new energy plants and urban substations. Internal arc faults inside closed switchgear equipment may trigger cabinet bursts and safety accidents. As a professional electrical switchgear manufacturer, Chuanli follows strict Switchgear Cabinet Manufacturing standards. This article combines IEC standards and Chuanli cabinet design data to analyze arc hazards, detection technologies and integrated suppression solutions for engineering practitioners.
The structure of the enclosed metal cabinet of the medium-voltage complete switch cabinet will greatly amplify the destructive power of arc faults. After a short-circuit arc occurs in the cabinet, the narrow and enclosed space cannot quickly vent and dissipate heat, causing a series of accidents due to the accumulation of energy in a short period of time.
When an arc fault occurs inside the l'appareillage électrique, the instantaneous temperature of the arc plasma exceeds 10,000°C, melting the copper busbar, burning the vacuum interrupter, and carbonizing the insulating parts; Under the action of high temperature, the gas in the cabinet expands violently and produces a huge impact pressure, which may open the cabinet door and the back cover, and spray the high-temperature molten metal and toxic flue gas into the operation channel, causing severe burns and electric shock injuries to the on-site maintenance personnel. For unmanned new energy power station switch equipment, the continuous arc burning will spread along the busbar to the entire cabinet, causing a large-scale power outage in the whole station and resulting in huge power generation losses; At the same time, after the arc extinguishes, the residual carbonized conductive attachment will adhere to the surface of the component, and the insulation breakdown hidden fault will recur in the later operation. The following table visually compares the difference in arc hazard between a normal non-arc cabinet and a complete set of arc suppression cabinets from Chuanli.
| Comparison Item | Standard Switchgear (Non-Arc-Resistant) | Chuanli Medium-Voltage Switchgear (Full Arc-Suppression System) |
| Maximum Arc Withstand Duration | ≤100ms (risk of enclosure deformation) | Meets IAC A FL (full-side access) 1s arc-withstand standard |
| Internal Pressure Relief Method | Single-layer thin sheet; single rear-panel blowout | Dual-path directional pressure relief (top + rear) |
| Arc Containment/Barrier Capability | Thin partitions easily burned through by arc | Independent compartments separated by 2.5mm thick steel plates |
| Fault Trip Response Speed | Conventional relay protection:> 300 ms | Dual-sensor linkage: ≤15ms (ultra-fast tripping) |
| Component Damage After Fault | Busbars and arc-extinguishing units completely ruined | Only localized sensor components require replacement |
Chuanli cabinet integrates a passive containment structure + active ultra-fast arc extinguishing device, which can limit arc energy to a single compartment, preventing it from spreading across cabinets, thus significantly reducing the cost of post-fault maintenance and the duration of power outages.
There are many causes of arc faults in medium-voltage switchgear, covering the whole process of cabinet manufacturing, on-site construction, and long-term operation. In the switch cabinet manufacturing process, the wiring process is not standardized, the multi-strand wire is not pressed with a copper nose, and the wiring terminal is loose, which will cause local overheating and carbonization, inducing arc discharge. Insufficient thickness of the cabinet compartment and poor sealing can also lay the groundwork for the spread of arcs. During the on-site installation and distribution of power, the fall of metal wire shavings and screws into the busbar room is the most common cause of sudden arcs; Under the condition of long-term operation, the condensation in the cabinet, the aging of insulation caused by long-term overload, the invasion of small animals, and the breakdown of lightning strike will gradually reduce the insulation performance of components, eventually evolving into a continuous short-circuit arc. For new energy feeder switchgear sets, the frequent bidirectional current and harmonic superposition will accelerate the aging of insulation sleeves, and such cabinets are more prone to arc hazards than ordinary municipal distribution switchgear.
Real-time precise capture of arc signal is the premise of rapid suppression of faults, and the whole arc protection system of Chuanli is equipped with two mainstream sensing schemes of optical flow double detection and pressure sound composite detection, which can be selected and matched according to different cabinet compartments and risk levels, and the paragraphs are continuous without splitting into small paragraphs.
The optical fiber arc sensor combined with the overcurrent current transformer forms the most widely used double-criterion detection scheme in the application of medium-voltage l'appareillage électrique, which can effectively avoid the mis-tripping caused by the single light and single current signal interference. The optical fiber sensing cable is laid along the top of each independent compartment of the cabinet, capturing the arc light signal as soon as the arc occurs. The current acquisition circuit collects the abnormal short-circuit current signal through the CT, and the protection relay only issues the opening command when the optical signal and the overcurrent signal are triggered simultaneously. This dual-criterion sensing configuration is the standard configuration for high-risk cabinets such as KYN28 in-line and busbars, and the fiber optic has strong anti-electromagnetic interference capability, which perfectly adapts to the complex harmonic conditions of new energy switchgear. The following table summarizes the mainstream arc sensing performance parameters of two sets of Chuanli switch cabinets.
| Sensing Solution | Core Detection Principle | Response Latency | Installation Location | Compatible Switchgear Type |
| Fiber-optic + Current Dual Detection | Dual criteria: Arc light + Sudden short-circuit current | ≤7ms | Busbar compartment, incoming feeder panel, main feeder panel | KYN28 metal-clad withdrawable switchgear |
| Pressure-Acoustic Composite Sensor | Internal pressure surge + Arc combustion noise | ≤15ms | Cable outgoing feeder panel, PT secondary compartment | XGN fixed-type switchgear assembly |
Fiber optic dual detection responds faster and is more resistant to interference, making it suitable for high-risk busbar areas. The cost of the pressure sensor is lower, and it is mainly used in low-risk secondary compartments such as cable rooms.
For low-risk compartments such as the cable room of the XGN fixed-type switchgear set and the PT room, the compressed sound composite integrated sensor from Chuanli is used as an economical alternative detection solution. When an arc is generated inside a sealed compartment, the instantaneous increase in pressure and the continuous high-frequency combustion noise will be captured by the integrated sensing module, and the signal will be uploaded to the arc protection relay to complete the judgment and disconnect. The sensor is fixed on the inner wall of the cabinet, and there is no need for complex fiber optic wiring construction, which makes the renovation of old switch cabinets convenient; However, this scheme is vulnerable to mechanical vibration interference from circuit breaker opening and closing, and must be paired with current auxiliary locking signals to reduce the probability of false operation. It is widely used in industrial park branch feeder XGN cabinet projects.
After receiving the arc detection signal, active quenching is the core technology for quickly suppressing the fault. The medium-voltage switchgear of Chuanli is equipped with two types of fast quenching devices according to the level of short-circuit current: a high-speed grounding short-circuit switch and a gas-producing quenching chamber. After the arc protection relay receives the double detection signal, it drives the grounding switch to complete the three-phase artificial short-circuit within 15ms, relying on the low impedance grounding circuit to quickly transfer the arc current and cut off the arc energy; The small and medium current distribution cabinet compartment is equipped with gas-producing arc extinguishing film, which detects the arc light and instantly releases high-pressure inert gas to cool and tear the arc plasma. The entire arc extinguishing and interlocking process is controlled within 20ms, which shortens the arcing time by more than 80% compared with the conventional disconnecting circuit breaker, and significantly reduces the degree of burnout of busbars and components. All the arc extinguishing devices of Chuanli have passed the 40kA short-circuit endurance test and can still be stable and repeatable after multiple arc faults.
The passive arc containment cabinet is the basic safety barrier of the complete set of switchgear. In the manufacturing stage of the complete set of switches, Chuanli optimizes the cabinet from three dimensions: compartment isolation, directional pressure relief, and high-temperature-resistant materials. The entire cabinet is divided into four independent sealed compartments by 2.5 mm thick steel plates, namely, the busbar room, the circuit breaker room, the cable room, and the secondary control room, and all the partitions are welded to block the spread of arcs across the compartments. The top and rear of each compartment are equipped with one-way blasting pressure relief plates, and the high-temperature gas generated by the arc can only be discharged upward and backward, preventing it from being sprayed into the front operating area, which fully meets the IAC A FL full facade internal arc test standard. All bus supports and compartment lining are made of high-temperature-resistant SMC composite insulating material, and high-temperature arc baking will not decompose conductive carbon, effectively avoiding secondary insulation failure after arc extinction. The cabinet frame is reinforced with multiple strengthening ribs to resist the instantaneous impact pressure of the arc and prevent the cabinet from swelling and deforming.
When configuring a complete arc suppression system for medium-voltage electrical switchgear, it is necessary to match the cabinet type, application scenario, and short-circuit current classification, and summarize five core selection specifications based on the experience of using products from Chuanli. First, the high-risk bus cabinet and input cabinet must be equipped with a complete set of optical fiber + current double detection + high-speed grounding arc extinguishing switch, and each bus section is independently equipped with a set of sensing modules to realize zone selective protection. Second, the low-risk cable outlet cabinet can be selected with the pressure sound composite sensor + the built-in gas-producing arc extinguishing plate, balancing the project cost and safety performance. Third, the new energy feeder switchgear needs to add an anti-harmonic filter module to the arc protection relay to prevent mis-tripping caused by bidirectional fluctuating distorted current. Fourth, all arc protection devices reserve the IEC 61 850 GOOSE communication interface, and fault signals can be remotely uploaded to the power plant SCADA monitoring system. Fifth, the cabinet must be selected through the IAC arc-resistant structure standard model of Chuanli, and the ordinary thin-plate cabinet without isolation can still explode after the arc fault even if it realizes the rapid opening of the circuit breaker; All the simulated short-circuit arc aging tests of the complete set of arc protection equipment are completed before the equipment leaves the factory, and the accuracy of the sensor, relay, and arc extinguishing equipment is verified.
Internal arc faults pose severe threats to switchgear. Chuanli builds a dual active-passive arc protection system for Assembled Switchgear Cabinets, relying on mature Armoire électrique assemblée Manufacturing. Select IAC arc-resistant cabinets with matched arc protection devices to cut outage losses and safeguard long-term stable operation of power distribution networks.
Q1: What kind of dual-detection arc sensing solution is standard on KYN28 bus switchgear from Chuanli?
A1 : The optical fiber arc sensor with short-circuit current transformer dual-criterion detection system has a response delay of < 7 ms.
Q2: What are the two core arc suppression technologies used in the medium-voltage complete switchgear of Chuanli?
A2 : Active high-speed arc extinguishing device + passive multi-compartment arc-resistant cabinet structure.
Q3: What kind of internal arc test standards can the complete set of Chuanli arc-resistant switch cabinets pass?
A3 : IEC 62272-200 IEC A FL 20 kA / 1 s full-face arc endurance test.
Q4: What kind of cabinet does the integrated soundproof arc sensor adapt to?
A4 : XGN fixed set cable outlet cabinet, PT secondary compartment low-risk area.
Q5: Why does the new energy feeder switchgear need a dedicated arc protection relay?
A5 : Add an anti-harmonic filtering function to prevent mis-tripping caused by bidirectional fluctuating distorted current.
