In the construction of new power systems, the intelligent upgrading of urban and rural power distribution networks, and the construction of industrial and commercial power distribution projects, high-voltage over-voltage protection is a core component for ensuring the stable operation of primary and secondary power distribution equipment and preventing power grid accidents. Zinc oxide surge arresters (MOAs), as the most widely used and stable nonlinear over-voltage protection devices in current power systems, are widely used in mainstream power distribution equipment such as high-voltage switch-gear, ring main units, pole-mounted vacuum circuit breakers, prefabricated substations, and main transformers. For power equipment manufacturers aiming to meet the grid connection standards of the State Grid and Southern Power Grid, comprehensive electrical performance testing of surge arresters is an indispensable core process in production quality control.
Shanghai Demiks Power Technology Co., Ltd. (DEMIKS POWER, website: www.demikspower.com), as a professional source manufacturer of high-voltage power testing equipment , has long been deeply involved in the fields of high-voltage insulation testing, lightning impulse testing, partial discharge testing, and special testing of electrical components. It has consistently supplied zinc oxide surge arrester testing equipment and complete sets of high-voltage testing equipment to industry enterprises in bulk, covering all scenarios of surge arrester factory inspection, whole-unit type testing, and on-site acceptance testing. It also provides one-stop value-added services such as on-site installation and commissioning, specialized operator training, industry standard technical exchanges, and lifetime equipment maintenance, helping power distribution equipment manufacturers build standardized and compliant high-voltage testing laboratories.
- Structure and Core Working Principle of Zinc Oxide Surge Arrester (MOA)
Zinc oxide surge arresters are mainly composed of four parts: a silicone rubber/ceramic insulating jacket, an internal zinc oxide nonlinear resistor sheet, a sealing structure, and upper and lower terminals. The core working medium is the zinc oxide ceramic resistor valve sheet, which has extremely strong nonlinear volt-ampere characteristics, and is also the core advantage that distinguishes it from traditional silicon carbide surge arresters.
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The equipment operates under two conditions: normal grid operation and fault over-voltage operation. Under the rated continuous operating voltage of the grid, the zinc oxide varistor exhibits extremely high insulation resistance, and the surge arrester is in a cutoff and dormant state, with only a weak leakage current in the microampere range flowing through it, consuming almost no electrical energy. When the line encounters lightning over–voltage, switch operation over–voltage, or system harmonic oscillation over–voltage , the instantaneous grid voltage spikes sharply, and the resistance of the zinc oxide varistor drops precipitously, rapidly conducting and discharging the massive surge current, clamping the line over-voltage within the insulation tolerance range of the downstream high-voltage equipment. After the over-voltage fault disappears and the grid voltage returns to normal, the varistor quickly returns to a high-resistance insulation state, stops discharging current, and the equipment returns to standby protection state.
Compared to traditional gap-type surge arresters, gapless zinc oxide surge arresters have advantages such as fast response speed, low residual voltage, large current capacity, no follow current, no daily maintenance, and suitability for intelligent power distribution scenarios. They have now completely replaced traditional surge arresters and become the only mainstream lightning protection component in high and low voltage power distribution systems.
- Application Scenarios and Core Uses of Zinc Oxide Surge Arresters
Based on Beijing Haochuang Ruitong Power’s main business and mainstream domestic power distribution engineering project scenarios, the applications of zinc oxide surge arresters can be divided into four major categories, basically covering all high and low voltage power complete equipment matching scenarios:
- 10kV distribution network system (largest usage and most mainstream scenario)
This voltage level is also suitable for mainstream power distribution network products , compatible with a full range of products including primary and secondary integrated pole-mounted vacuum circuit breakers, KYN28 high-voltage switch-gear, XGN ring main units, prefabricated substations, and cable branch boxes. It is available in indoor cabinet-mounted and outdoor pole-mounted types: outdoor pole-mounted surge arresters are mainly installed on overhead power line poles to protect pole-mounted switches, line insulators, and cable terminals from lightning strikes; indoor enclosed surge arresters are installed inside switch-gear and prefabricated substation enclosures to protect busbars, voltage and current transformers, and integrated protection secondary equipment, suppressing operational overvoltages within the distribution cabinet.
- Protection of main equipment in high-voltage substations (35kV-500kV)
It is used in public substations and industrial hub substations, and is equipped with main transformers, GIS switch-gear, high-voltage busbars and parallel capacitor banks. As the first-level lightning protection equipment for the whole station, it prevents insulation breakdown accidents of high-voltage main equipment due to lightning strikes and system operation over-voltages, and ensures the safe operation of core equipment in the substation.
- Special power distribution scenarios for new energy sources
Widely used in centralized photovoltaic power stations, wind power stations, and energy storage substation charging pile systems; new energy power stations have complex harmonics and frequent over-voltage faults, and surge arresters mainly undertake the lightning protection of converters and step-up transformers, solving the problem of unstable over-voltage in new energy power grids.
- High-risk power distribution scenarios in rail transit and industry
It is used in railway traction substations, large chemical industrial parks, and mining power distribution systems, providing over-voltage protection for impulsive load scenarios and resisting operational over-voltages caused by frequent start-stop of industrial equipment.
Summarize the core value of the equipment
Zinc oxide surge arresters are the “safety pressure relief valves” of the power system. Once the surge arrester itself fails to keep its insulation, the valve plate ages, or the inside becomes damp, it will directly cause the switch cabinet to explode, the line to short-circuit, the transformer insulation to burn out, and the area to go black. In severe cases, it may cause the surge arrester to explode and catch fire. Therefore, strict high-voltage testing during the production stage is the core means of controlling product quality and avoiding power grid operation accidents.
III. Mandatory Requirements of National Standards: Full-Level Testing Items for Zinc Oxide Surge Arresters (GB/T 11032-2020)
According to the national mandatory standard GB/T 11032-2020 AC gapless metal oxide surge arresters, and in conjunction with the State Grid equipment grid access acceptance specifications, surge arrester testing is divided into three categories: factory routine testing, on-site acceptance testing, and third-party type testing . Shanghai Demex Electric can supply all types of testing equipment for all three categories, and all equipment has been put into production and use in the laboratories of power equipment manufacturers .
(a) Routine factory tests (mandatory for every finished product, full inspection on the production line)
Factory testing is a 100% inspection item for manufacturers, screening out unqualified and deteriorated products. It is adapted to batch production quality inspection in the workshop, and the core relies on the DEMIKS DYX series (DEMIKS POWER ZnO Surge Arrester Tester) zinc oxide surge arrester comprehensive testing system to complete a full set of tests.
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- DC reference voltage (U₁mA) test : The surge arrester is continuously boosted, and the critical voltage under a 1mA DC reference current is collected to determine the overall nonlinear performance of the zinc oxide varistor. If the numerical deviation exceeds ±5%, the product is directly judged as unqualified.
- 0.75U₁mA DC leakage current test : The industry’s most critical quality control indicator. The voltage is boosted to 0.75 times the DC reference voltage to detect the microampere-level steady-state leakage current; it is mainly used to determine the sealing performance of the surge arrester and to check for internal moisture and water ingress defects in the cavity.
- Power frequency reference voltage and resistive current test : Simulate the long-term power frequency operation conditions of the power grid, and test the total current, resistive current and capacitive current of the surge arrester; if the resistive current exceeds the standard, it is directly determined that the valve plate is aging and it is prohibited to send it out of the factory and connect it to the grid.
- Insulation resistance test and appearance sealing inspection : High-voltage megohmmeter is used to screen for insulation faults in large components, and the outer skirt and flange sealing structure are checked to prevent products with damaged appearance from entering the market.
(ii) On-site handover test (pre-installation and commissioning testing)
After the surge arrester is installed along with the switchgear and pole-mounted switch, the power grid acceptance personnel will conduct on-site retesting. The items include: insulation resistance testing, DC U1mA and leakage current retesting, three-phase current balance comparison, and live full current monitoring; to ensure that there is no equipment damage during transportation and installation.
(III) Type testing (full high-voltage test for new product network access and qualification certification)
Type testing is a destructive, full-scale high-voltage test used for product inspection and State Grid qualification registration. It requires a complete set of large-scale high-voltage testing equipment from DEMIKS and is an essential laboratory configuration for power distribution companies building their plants.
- Insulation withstand voltage test: short-time power frequency withstand voltage test, switching impulse withstand voltage test (supporting equipment: frequency converter series resonant withstand voltage device, power frequency test transformer);
- Lightning impulse series tests: standard lightning wave impulse, steep wave impulse, and residual voltage characteristic test (supporting equipment: fully automatic lightning impulse voltage generator).
- Partial discharge test: Detection of micro-discharge under operating voltage to check for internal insulation bubbles and hidden cracks (equipment: multi-channel fully automatic partial discharge test system).
- Durability and mechanical performance tests: high current impact resistance test, thermal stability aging test, bending mechanical strength test, and resistance test to humid and polluted environment.
- Demix: Cooperation Plan for Testing Equipment of Benchmark Power Distribution Enterprises
Shanghai DEMIKS Power provided all manufacturers of zinc oxide surge arresters with [supporting equipment] . We offer a one-stop shop for comprehensive surge arrester testing and high-voltage power testing equipment , covering complete sets of power distribution equipment including primary and secondary integrated pole-mounted switches, high and low voltage switchgear, ring main units, and prefabricated substations. .
The supplied equipment covers the entire process of surge arrester testing and all aspects of insulation/partial discharge/lightning strike testing for complete switch-gear, perfectly matching the quality inspection needs of its entire 10kV power distribution product line. Unlike ordinary equipment suppliers, DEMIKS leverages its source factory’s R&D and production advantages to provide power distribution equipment manufacturers with a complete closed-loop value-added service chain.
First, nationwide on-site installation and commissioning: professional high-voltage engineers will come to your site to complete equipment placement, wiring calibration, and laboratory condition connection, so that the equipment can be put into production and used immediately upon arrival at the site;
Second, on-site practical training: one-on-one specialized training for enterprise quality inspection personnel on equipment operation, national standard testing procedures, and data report generation;
Third, targeted technical exchanges: Free technical seminars will be held on topics such as interpretation of power industry testing standards, fault analysis of non-conforming products, and overall laboratory layout solutions.
Fourth, full-cycle after-sales maintenance: lifetime technical consultation for equipment, regular on-site inspections and calibrations, expedited fault repairs, and upgrades and renovations for old equipment.
- Conclusion: Why do power distribution manufacturing companies choose DEMIKShigh-voltage testing equipment?
From component testing of zinc oxide surge arresters to type testing of high-voltage complete power distribution systems, standardized, high-precision high-voltage power testing equipment is indispensable for the quality inspection of power equipment before it leaves the factory. As a long-term cooperative supplier of leading power distribution manufacturers in the industry, Shanghai Demiks Power Technology Co., Ltd.’s entire series of equipment has undergone front-line production line operation verification and fully complies with the State Grid and national standard testing standards; it is compatible with all manufacturers of high and low voltage complete switch-gear, power equipment, and surge protection components.
Any power industry enterprise that needs to build a high-voltage testing laboratory or purchase specialized testing equipment for insulation withstand voltage, partial discharge, lightning impulse, and surge arresters can contact Shanghai DEMIKS Power. We provide a one-stop integrated solution from laboratory layout, equipment supply, on-site commissioning, personnel training to qualification and acceptance testing.
Official website: www.demikspower.com
