Where Is The NGR System Installed On The Transformer?

An NGR (neutral Neutral Grounding Resistor) system is usually installed between the neutral point and grounding point of the transformer. The specific location depends on the transformer's installation scenario (indoor or outdoor) and the system's grounding requirements. Installation locations are detailed below:
Core Logic for Installation Location
The NGR's core function is to limit neutral ground fault currents with a series resistor. Therefore, the neutral point of transformer must be directly connected to the ground. For example, in a 10kV transformer, neutral points are connected to the ground grid in series to ensure that fault currents is not limited by the resistor before grounding.
Indoor Installation Scenario
Substation or Distribution Room: A substation or distribution room is usually located next to an indoor transformer and installed in a special cabinet on the side of the transformer's neutral point. For example, in a 6-35kV urban distribution network, the NGR cabinet can be installed directly next to transformers and connected to neutral points through copper busbars or cables.
Protection Requirements: Indoor environment must be IP23 or above to prevent dust and moisture intrusion, and cabinet material must be corrosion resistant. Outdoor Installation Scenario
Vertical transformers or open substations: NGR can be connected to a neutral point by short cables using separate outdoor cabinets installed near the transformer foundation. For example, in some industrial parks or rural power grids, the NGR cabinet can be connected directly to transformer stands.
Environmental Adaptability: Outdoor cabinets must be IP54 or higher protected, with accessories such as rain covers and dust mesh to protect against severe weather.
Installation Flexibility
Wiring Options: NGR cabinet support multiple connectivity options, including top-down, top-down and self-side-down, self-side-down, allowing flexibility based on site space and wiring requirements. For example, when space is limited, you can reduce the size of a building by using a side in / side out configuration.
Modular Design: Some NGR products have modular structures that can independent replacement resistor units, monitoring equipment and other components for future maintenance and capacity expansion. Real-world case studies
10kV Transformer Applications: In a certain city's 10kV distribution network, substations have an NGR cabinet. By connecting the copper busbar to the transformer neutralization point, the fault current is limited to 100 A. Zero-sequence current transformers can also be used to select fault line selection.
35kV Power Plant Application: A power plant's 35kV auxiliary power system utilizes an outdoor NGR. The box body is mounted next to the transformer foundation and is connected with a neutral point by a short cable. The design load time is 10 seconds to satisfy relay protection requirements.