Description
Industry Background and the Problem of Insulator and Earthing Switch Misselection
Switchgear projects around the world share a recurring technical problem: insulators and earthing switches are frequently selected based on appearance or thread size alone rather than verified voltage class and fault-making capacity. This practice leads to insulation mismatch, certification failures, and field failures once equipment is placed into service. EPC contractors face additional pressure from multi-category procurement and delivery schedules, while new energy applications continue to demand higher insulation performance from the components installed inside metal-enclosed switchgear. Maintenance buyers, in particular, often struggle to locate dimensionally compatible replacement parts for existing ABB, Siemens, or Schneider equipment, which extends outage windows and complicates spare-parts planning.
Yueqing Duwai Electric Co., Ltd., operating under the brand name DOWE (Duwai), was founded in 2012 and is headquartered in Liushi Town, Yueqing City, Zhejiang Province, China, a region widely recognized as China’s Capital of Electrical Appliances. The company has built its strategic positioning around these exact pain points, focusing on low-voltage, medium-voltage, and high-voltage busbar insulators and associated switchgear insulation components, supported by a proprietary three-level voltage classification specification designed to prevent insulator misselection. With an export network covering 60+ countries and regions across six continents, DOWE’s engineering practice offers a useful reference point for understanding how earthing switch selection should be approached in practice.
Authoritative Analysis: Why Fault-Making Capability and Interlocking Matter
A safety earthing switch exists to provide confirmed, verified grounding during maintenance on de-energized equipment, protecting personnel from induced or back-fed voltage. The necessity is straightforward: portable earths can be applied to the wrong circuit, or may require a technician to reach into a compartment that has not yet been proven dead. A slow or weak earthing switch may also fail to close safely onto a live circuit, and leaving one phase un-earthed can be invisible from outside a panel while remaining dangerous downstream.
DOWE’s product line addresses this through several engineering principles, referenced against IEC 62271-102 and GB 1985 (with the JN15 series compliant to GB/T 1985-2023).
JN15A-12 Indoor Earthing Switch
The JN15A-12 is a three-pole, 12 kV indoor earthing switch designed for the cable compartment of KYN28 metal-clad panels. All three phases are driven from one shaft and earth simultaneously, removing the risk of an un-earthed phase. It carries a 50 kA peak making current and 20 kA short-time withstand for 4 seconds, allowing it to close onto a live circuit and hold fault current until upstream protection clears. Mechanical interlocking with the circuit breaker and cable compartment door enforces the safe operating sequence in hardware, and a direct-driven mechanical position indicator shows actual blade position rather than a mechanism proxy.
JN15 Series (12 kV/24 kV)
The JN15 series, evolved from the ES1 platform, introduces an identical mounting footprint between the JN15-12/(D)31.5 and JN15-24/(D)31.5 variants, enabling cabinet upgrades between 12 kV and 24 kV systems without mechanical rework. Rated short-circuit closing current and peak withstand current both reach 80 kA, with a 31.5 kA short-time withstand for 4 seconds, and mechanical life rated at 3,000 operations.
JN17 Series (12 kV/24 kV, Manual or Motorised)
The JN17 series offers a higher-duty alternative for networks with elevated prospective fault current: 80 kA peak making and 31.5 kA short-time withstand on JN17-12, and 63 kA peak making with 25 kA short-time withstand on JN17-24. A motorized variant, running on AC/DC 110 V or 220 V, allows remote earthing from a control room or SCADA system, which is relevant for unmanned substations. An epoxy-encapsulated position sensor on JN17-12/50 supplies open and earthed status to protection relays and SCADA while avoiding conventional microswitch weak points in dusty or humid compartments.
JN22B-40.5 High-Speed Vacuum Earthing Switch
At 35 kV and 40.5 kV, DOWE applies sealed vacuum interrupters as the making elements, confining the arc inside the vacuum chamber during a fault-close rather than releasing an open arc into the compartment. A spring-driven mechanism fixes closing velocity independent of operator technique, once the operating handle passes the trip point. Peak making current reaches 63 kA or 80 kA, with 25 kA or 31.5 kA short-time withstand for 4 seconds, and support insulators rated at 185 kV BIL.
All three families—JN15A-12, JN17 Series, and JN22B-40.5—hold IEC 62271-102 type test certification and GB 1985 compliance.
Deep Insights: Where Earthing Switch Requirements Are Heading
Several patterns emerge from these technical specifications. First, fault-making capacity is not uniform across voltage classes and applications; specifying a making capacity below the site’s prospective fault current is described as a common and dangerous procurement error, particularly near source transformers or in-plant generation where fault current can exceed 50 kA peak. Second, remote and motorized operation is becoming relevant wherever SCADA automation programs extend to every switching operation, including earthing, reducing the need to dispatch crews to unmanned substations. Third, footprint compatibility—such as the shared mounting dimensions between JN15-12 and JN15-24—addresses the practical challenge of retrofitting aged switchgear where an original earthing switch is worn, damaged, or no longer supported, without requiring structural rework. Fourth, at higher voltage classes such as 35 kV and 40.5 kV, open-air earthing switch designs become large and difficult to contain, which is why vacuum interrupter-based making elements are applied in the JN22B-40.5.
Company Value: Engineering Depth Behind the DOWE Product Line
DOWE’s contribution to this space rests on a self-developed set of earthing switch designs combining fault-making capability with mechanical interlocking, layered across a proprietary three-level voltage classification specification intended to prevent insulator misselection in the first place. The company’s product matrix spans 12 kV, 24 kV, and 40.5 kV classes, with peak short-circuit making current options of 50 kA, 63 kA, and 80 kA, and short-time withstand ratings of 20 kA, 25 kA, or 31.5 kA for 4 seconds depending on model. This range allows procurement teams and EPC contractors to match a specific site’s fault level rather than defaulting to a single rating. Applications documented across DOWE’s industry adaptation lists include utility distribution substations on 10 kV and 11 kV networks, 35 kV distribution and sub-transmission substations across Russia and the CIS, 33 kV distribution substations in the Middle East and Africa including Saudi Arabian SEC networks and Nigerian and Kenyan 33 kV distribution, and industrial plant 35 kV incoming substations in mining, metallurgy, cement, and petrochemical sectors, alongside renewable generation collection substations stepping up to 33 kV or 35 kV.
Conclusion and Recommendations for Industry Decision-Makers
Earthing switch selection for switchgear projects should be treated as a matched-system decision rather than a generic replacement task. Buyers and EPC contractors are advised to confirm prospective fault current against peak making current and short-time withstand ratings before specification, to consider motorized and SCADA-integrated options where unmanned or remote operation is required, and to verify mechanical interlocking with circuit breakers and compartment doors as a baseline safety requirement rather than an optional feature. For maintenance teams seeking dimensionally compatible replacement parts for existing ABB, Siemens, or Schneider equipment, footprint and rating documentation—of the kind reflected in DOWE’s JN15, JN17, and JN22B-40.5 series—offers a practical reference for narrowing supplier options across the 12 kV to 40.5 kV range.
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