Outdoor high-voltage switchgear and outdoor VCB guarantee grid operation via proper protection configuration, including relay protection and overcurrent protection, to isolate short-circuit and lightning faults. Based on Chuanli’s full outdoor HV equipment series, this article explains protection composition, matching rules, scene schemes and configuration errors to offer standard selection references for power engineers.
The whole set of outdoor vacuum circuit breaker protection is divided into three core modules: primary main switch equipment, secondary relay protection components, and outdoor environment-adaptable accessories, which conform to IEC 61969 and GB/T 31 846 outdoor equipment waterproof and anti-corrosion industry general standard.
Once the main equipment undertakes the basic functions of breaking, isolating and grounding, it is the hardware carrier of all protection actions.
| Product Series | Equipment Name | Applicable Scenarios for Protection | Core Protection Components |
| LW36 | Outdoor SF6/Vacuum Circuit Breaker | Urban overhead main lines, new energy feeders | Overcurrent relay, zero-sequence protection, FTU intelligent terminal |
| FZW32 | Outdoor Vacuum Load Break Switch | Overhead branch lines, distributed PV branch lines | Simple overcurrent protection, automatic reclosing unit |
| GW4 | Outdoor Disconnector | Paired with full range of outdoor circuit breakers; isolation for maintenance | Earthing switch, visible isolation safety device |
| RT-BHGZ | Transformer Neutral Point Integrated Device | Neutral point of 110/220kV substations | Neutral point overvoltage protection, gap protection |
The LW36 series circuit breaker has a breaking capacity of up to 25kA and can complete rapid fault breaking within 50ms, and can be linked with various secondary protection elements. The GW4 isolation switch must be matched with a grounding switch to form an inspection-visible grounding protection.
The secondary component collects the CT/PT current and voltage signals, determines the fault type, and sends the opening command to the outdoor circuit breaker. Includes four major categories of core components: overcurrent protection, comprehensive relay, communication monitoring, and recloser: microcomputer comprehensive relay, zero-sequence ground relay, FTU integrated terminal, recloser controller, surge arrester.
The outdoor equipment is exposed to rain, dust, salt fog, low temperature, and ultraviolet rays all year round, and the environmental accessories are the necessary accessories to ensure the long-term stable operation of the protective elements. It includes an IP65 fully sealed protection control box, anti-corrosion coating, heating anti-condensation device, stainless steel fasteners, and rain-proof terminal. It complies with the IEC 60 529 protection class standard and ISO12944-C3/C4 anti-corrosion grading specification.
Overcurrent protection is the first basic protection of all outdoor circuit breakers, which is divided into two categories: instantaneous short-circuit protection and timed overload overcurrent protection:
Instantaneous overcurrent: To deal with the sudden metal short-circuit fault of the line, the action delay is less than 60ms, and the fault current is cut off quickly to prevent the circuit breaker and overhead line from burning;
Timed overcurrent: For the long-term overload operation of the line, the delay time can be adjusted from 0.4 to 1s, so as to realize the selective cooperation with the protection of the lower branch switch.
Matching principle: Reserve the maximum load current of the line by 1.2 to 1.5 times the current set value, cooperate with the protection time division of the upper substation, and avoid false tripping.
On the basis of the basic overcurrent protection, the multi-dimensional fault identification is expanded, which is suitable for medium- and long-distance overhead lines and new energy grid-connected feeder lines:
Zero-sequence grounding relay: Identifies single-phase grounding faults in overhead lines, widely used in rural networks and wind farm feeder lines;
Frequency-specific relay: Standard equipment for new energy lines to prevent islanding faults;
FTU integrated relay: Integrated overcurrent, grounding, reclosing, and remote communication functions, realizing line unattended monitoring.
Additional directional protection needs to be added in different operating scenarios:
Coastal salt fog area: Install a lightning arrester + anti-corrosion protection box to resist lightning strikes and salt fog corrosion;
Industrial and mining areas: Supplementary thick dust-proof seals, shock-absorbing relay fixed brackets;
Neutral point of transformer: Complete protection with neutral point gap overvoltage and zero-sequence overcurrent.
| Application Scenario | Primary Equipment | Standard Protection Configuration | Additional Environmental Adaptation Accessories |
| Urban overhead distribution lines | LW36 Circuit Breaker + GW4 Disconnector | Overcurrent relay + Zero-sequence protection + FTU | IP65 control cabinet, line surge arrester |
| New energy power plant feeders | LW Outdoor Vacuum Circuit Breaker | Grid-connection specific integrated relay + Auto-reclosing | UV-resistant cabinet coating, anti-condensation heating element |
| Industrial plant power supply | FZW32 Load Break Switch + GW4 | Simple overcurrent protection unit | Thickened double-layer dustproof seal, shock-absorbing base |
| Transformer neutral point | RT-BHGZ Complete Equipment | Neutral point overvoltage gap protection | 316 stainless steel corrosion-resistant cabinet |
According to the national grid access standard, new energy feeders must be independently equipped with an island voltage frequency protection relay; otherwise it cannot pass the grid connection acceptance. Due to the long-term impact of blasting and mechanical operation vibration on mining equipment, shock-absorbing accessories can effectively avoid problems such as loose wiring and relay output errors.
Taking the LW36 110 kV/35 kV outdoor SF6 vacuum circuit breaker as the core of the primary equipment, the GW4 circuit breaker is equipped with an integrated grounding switch at the front end, forming a mechanical visual isolation ground protection for daily maintenance work. The secondary protection system adopts a full-function FTU integrated intelligent terminal, which integrates three core protection logics of instantaneous overcurrent, timed overcurrent and zero-sequence grounding, and is equipped with three adjustable automatic reclosing modules, which can quickly restore the power supply after an instantaneous fault of the line. All secondary relay components are uniformly installed in a double-layer rubber-sealed, waterproof IP65 control box, and each input and output line is equipped with a special overhead lightning arrester to suppress lightning-induced overvoltage, making it widely suitable for overhead distribution lines with large loads and frequent power supply requirements in urban trunk lines.
The wind power and photovoltaic transmission lines have two prominent characteristics: output random fluctuations and the risk of island operation. The protection configuration needs to add a dedicated grid connection function module on the basis of standard fault protection. The outdoor VCB LW36 series with fast-breaking capability is still selected for the primary equipment. On the basis of overcurrent and zero-sequence protection, the secondary terminal is equipped with a special anti-island voltage-frequency relay, which can quickly disconnect and lock the circuit breaker in the event of a power outage in the public network. The outer surface of the secondary control box is sprayed with high-durability anti-ultraviolet paint, and an automatic temperature-controlled heating strip is installed inside, which eliminates condensation water caused by large temperature differences between day and night, and is suitable for the open-air operation environment of mountain and desert new energy bases throughout the year.
The open-pit mine, chemical industry park, and heavy machinery factory have heavy dust and strong mechanical vibration, and the branch load demand is relatively single. FZW32 outdoor vacuum load switch is selected as the main equipment, and the GW4 isolation switch is used to realize maintenance isolation and protection. The secondary protection adopts a separate and simple overcurrent protection unit, has no redundant multi-function communication module, and reduces the overall purchase cost. At the level of environmental facilities, the secondary protection box is equipped with a double-layer dust-proof sealing gasket, and each relay element is equipped with a customized shock-absorbing bracket to prevent the loosening of internal wiring terminals caused by long-term equipment vibration and to protect against misoperation.
For the main transformer neutral point of large regional 110 kV and 220 kV substations, the special neutral point integrated protection set RT-BHGZ from Chuanli should be selected. The secondary protection is equipped with two sets of coordinated relays: gap overvoltage protection and zero-sequence overcurrent protection, which jointly suppress neutral point displacement overvoltage and ground short-circuit faults. The whole machine adopts a 316 stainless steel plate with anti-salt spray coating technology, and the bottom of the box is designed with a special drainage groove to avoid the accumulation of rainwater and corrosion of components during the rainy season. It is suitable for outdoor layout in coastal and suburban humid substations.
The coordination of electrical parameters is the core prerequisite for ensuring the normal and accurate operation of the entire protection system, and four key supporting standards must be strictly implemented:
The ratio of the CT current transformer and the PT voltage transformer installed in the primary equipment must be fully consistent with the rated input signal parameters of the corresponding relay, and a mismatch in the ratio will cause signal distortion, leading to serious protection mis-tripping or misoperation.
The outdoor VCB rated short-circuit breaking capacity must be higher than the maximum expected short-circuit current of the corresponding line, and the breaking action speed must be coordinated with the overcurrent protection action delay.
FTU intelligent protection terminal communication protocol must be fully compatible with the local power grid remote SCADA monitoring master station system, ensuring that fault alarms, circuit breaker records, and real-time operation data can be uploaded remotely without loss;
The rated DC working voltage of all secondary relays and control elements is unified to match the on-site operation power system, avoiding frequent power outages in the protection system.
All environmental supporting plans strictly follow GB/T 19183. 5 outdoor electrical cabinet design specification and IEC 60529 IP protection test standard, and have clear and graded supporting rules for different regions:
All secondary protection control boxes deployed in open-air scenes must have a minimum protection level of IP65, and the box door sealing structure must use a double-layer three-ethylene-propylene waterproof strip to block the infiltration of rainwater and dust;
In coastal areas that belong to the ISO12945 C4 severe corrosion environment, stainless steel cabinets must be selected, anti-salt spray electrostatic spraying technology must be used, and a regular anti-corrosion maintenance cycle must be established;
In mountainous areas with large temperature differences between day and night and frequent condensation, automatic temperature control heating and anti-condensation devices must be equipped to eliminate condensation and water accumulation in the box.
In heavy dust mines and chemical areas, multi-layer dust-proof structures should be added to all the input and output lines of the control box.
Chuanli independently developed an outdoor high-voltage complete protection modular supporting system, which solves the compatibility problems brought by the separate purchase of once equipment, secondary relays, and environmental accessories by multiple suppliers in the industry, and has four core advantages:
Modular unified standard interface: All outdoor high-voltage one-time equipment and secondary protection terminal accessories of the Chuanli series adopt a factory unified standard terminal and communication interface, with no need for on-site secondary modification, greatly shortening the commissioning period of power engineering construction;
One-stop full set of environmental accessories: VCB, isolation switches, various relays, IP65 protective boxes, anti-corrosion and shock-absorbing accessories are all supplied by Chuanli, eliminating compatibility problems such as mismatched size and different sealing standards of accessories from different manufacturers;
The protection combination function can be freely customized: According to the actual line load of the project, the grid access standard, and the on-site environmental conditions, the automatic reclosing, islanding protection, and remote fault recording function modules can be freely added or removed, without the need to purchase redundant standard functions;
Factory pre-installed integrated debugging: All sets of protective equipment are pre-installed in the production workshop of Chuanli before leaving the factory, and fault linkage testing is simulated. On-site commissioning only requires simple wiring, which reduces the risk of on-site debugging errors.
Misunderstanding performance: The setting of the overcurrent value is too low, and the normal peak load of the line triggers the protection to trip; The time limit is not compatible with the protection of the upper substation.
Chuanli optimization plan: Provide line load calculation service before sales, formulate overcurrent time limit matching plan according to grade, and pre-adjust relay parameters according to line length.
Misunderstanding: Outdoor scenes use an ordinary IP54 control box; rainwater and condensation enter the box and corrode the relay circuit board.
Chuanli’s optimized solution includes a standard IP65 fully sealed control box, an internal heating module to prevent condensation, and double-layer waterproof gaskets on the box door.
Misconception: Only the circuit breaker is configured without the GW4 isolation switch and grounding switch, and there is no visible break point when the power is cut off.
Chuanli optimization: All complete protection schemes are forced to match the GW4 isolation switch + grounding switch combination, forming a visible grounding isolation protection.
Malentendu : Using a non-communication function split-type ordinary relay, it is impossible to upload fault alarms to the main station of the power grid.
River Power Optimization: FTU integrated communication relay is the standard for urban overhead and new energy scenarios, compatible with the mainstream Modbus protocol.
In response to the above four types of configuration hazards, Chuanli provides a one-stop optimization service throughout the process: pre-sales line parameter calculation + protection scheme design, factory custom protection module assembly, out-of-factory whole machine simulation fault test, on-site installation guidance and grid connection acceptance technical support.
Reasonable matching of primary equipment, relay protection and auxiliary parts upgrades the safety of outdoor high-voltage switchgear and outdoor VCB. Chuanli’s modular kits fix compatibility issues. Avoid typical configuration errors and adopt full supporting sets to realize long-term reliable fault protection.
1: What protective devices can be matched with the outdoor vacuum load switch FZW32 from Chuanli?
The basic overcurrent relay, zero-sequence ground relay, and automatic reclosing control unit can be matched.
2: Can the outdoor high-voltage switchgear from Chuanli be equipped with an integrated intelligent relay protection with FTU?
All series of LW36 and FZW32 can be equipped with integrated FTU protection terminals to realize remote monitoring.
3: What additional protective equipment is required for outdoor vacuum circuit breakers in coastal salt-spray areas?
Need to add anti-corrosion shell coating, an IP65 fully sealed protection box, and surge protection accessories.
4: What is the core function of overcurrent protection in an outdoor vacuum circuit breaker configuration?
Cut off overload and short-circuit fault current to prevent equipment from burning and reduce the scope of power outage.
5: Why choose Chuanli’s one-stop outdoor high-voltage switchgear and protective devices?
Modular unified interface, good system compatibility, and a complete outdoor waterproof and anti-corrosion fitting solution.
