{"id":31219,"date":"2026-02-18T09:30:00","date_gmt":"2026-02-18T09:30:00","guid":{"rendered":"https:\/\/www.engineernewsnetwork.com\/blog\/?p=31219"},"modified":"2026-02-16T11:33:39","modified_gmt":"2026-02-16T11:33:39","slug":"how-high-resistance-grounding-keeps-data-centres-online","status":"publish","type":"post","link":"https:\/\/www.engineernewsnetwork.com\/blog\/how-high-resistance-grounding-keeps-data-centres-online\/","title":{"rendered":"How high-resistance grounding keeps data centres online"},"content":{"rendered":"\n

Mike Torbitt explores how neutral earthing resistors enable data centres to treat first earth faults as alarm-only events, maintain continuous operation and demonstrate grid-friendly performance under the new readiness-based requirements. It also outlines how well-specified NERs support resilient, predictable operation as demand on infrastructure continues to grow<\/strong><\/p>\n\n\n\n

In December 2025, the UK’s National Energy System Operator (NESO) announced the results of its major overhaul of the UK’s grid connection process, removing speculative schemes and introducing a readiness-based system. While this affects all electricity projects, it raises the bar for data centres, which must now demonstrate grid\u2011friendly behaviour from day one. Neutral earthing resistors (NERs) can support resilient, grid\u2011compatible operation.<\/p>\n\n\n\n

Data centres have been recognised as Critical National Infrastructure (CNI) since September 2024, placing them on \u201can equal footing with water, energy and emergency services systems\u201d<\/strong><\/a>. While this recognition is invaluable to scaling capacity, NESO\u2019s reforms add a new layer of complexity.<\/p>\n\n\n\n

The Connections Reform context<\/strong><\/p>\n\n\n\n

Under the Connections Reform<\/strong><\/a>, NESO now prioritises \u201cfirst ready and needed,\u201d replacing the former first\u2011come, first\u2011served approach. Many transmission-connected demand projects – including data centres – have been placed into firm capacity blocks with connection dates extending to 2035, reflecting a more realistic delivery timeline than the prior ambition to connect the full pipeline by 2030. In this context, fault management and predictable, grid\u2011friendly operation become prerequisites for connection.<\/p>\n\n\n\n

The readiness framework is evidence\u2011based. To secure a firm offer, developers must prove deliverability and true grid readiness \u2014 not just on paper, but through design maturity, risk controls and credible delivery plans. A robust power and protection strategy is therefore critical, showing the facility will behave predictably during network disturbances and will not trigger unnecessary disconnections.<\/p>\n\n\n\n

What is high-resistance grounding?<\/strong><\/p>\n\n\n\n

One mechanism central to grid\u2011friendly design is high\u2011resistance earthing, also known as high\u2011resistance grounding (HRG). Although industry benchmarking shows overall outages are declining, Uptime Institute<\/strong><\/a> data indicates power remains the leading cause of impactful incidents when failures do occur, cited by 54% of operators surveyed would be more accurate to the Uptime Institute’s methodology.<\/p>\n\n\n\n

In HRG systems, the transformer or generator neutral is connected to earth through a high\u2011value resistor. By introducing resistance, HRG limits single\u2011line\u2011to\u2011earth fault current to a small, controlled value \u2014 typically a few amps at low voltage or tens to hundreds of amps at medium voltage. The outcome is that a first earth fault becomes an alarm\u2011only event rather than an immediate trip, enabling continued operation while teams quickly locate and clear the fault.<\/p>\n\n\n\n

This approach avoids the drawbacks of other schemes. Unlike solid earthing, it prevents very high single\u2011line\u2011to\u2011earth currents and the associated incident energy, and unlike ungrounded systems, it keeps the neutral referenced, suppressing transient overvoltages and making faults easier to locate.<\/p>\n\n\n\n

Proper HRG design sets the resistor so the permitted fault current is above the system\u2019s capacitive charging current, yet low enough to reduce equipment stress and arc flash energy for single-line-to-earth faults. In data centres, this keeps the first earth fault \u2018alarm\u2011only\u2019, sustaining critical services while teams rapidly pinpoint the faulted feeder, avoiding nuisance trips across uninterruptible power supply and generator transitions and supporting grid\u2011friendly operation in the high\u2011density, always\u2011on environment.<\/p>\n\n\n

\n
\"\"<\/a>
Well-specified NERs support resilient, predictable operation as demand on infrastructure continues to grow. Image: Cressall Resistors<\/figcaption><\/figure>\n<\/div>\n\n\n

The critical component<\/strong><\/p>\n\n\n\n

An N<\/strong><\/a>ER<\/a> <\/strong>is the enabling component of a HRG system because it connects the neutral point to earth through a precisely selected resistance. By setting the resistance value correctly, the NER establishes the single\u2011line\u2011to\u2011earth fault current and the associated thermal duty so that protection relays can reliably detect a first fault without forcing an immediate trip. This behaviour keeps the system stable during disturbances and allows operators to locate and clear faults while maintaining service continuity.<\/p>\n\n\n\n

For data centres, NERs must be engineered to match real\u2011world constraints such as footprint, access routes for installation and maintenance, cooling and ventilation needs, and compliance with relevant international electrical standards. Cressall\u2019s designs prioritise ease of maintenance, high thermal performance and long service life so that facilities can run continuously and recover predictably after fault events or tests.<\/p>\n\n\n\n

Selecting the right resistor element is central to performance and cost. Edge\u2011wound coils are suited to higher currents, while grid and wire-wound elements serve other ratings efficiently. Cressall manufactures NERs across essentially any system voltage and initial fault\u2011current requirement, with rated durations ranging from a few seconds to continuous duty, so that specifications can align with the site\u2019s protection guidelines and operational objectives.<\/p>\n\n\n\n

Now that grid connections have been reprioritised, well\u2011specified NERs within HRG schemes make the first earth fault a managed, alarm\u2011only condition, keeping services online, demonstrating grid\u2011friendly behaviour and helping ensure data centre designs do not delay connection.<\/p>\n\n\n\n

Mike Torbitt is Managing Director of\u00a0Cressall Resistors<\/strong><\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"

Mike Torbitt explores how neutral earthing resistors enable data centres to treat first earth faults as alarm-only events, maintain continuous operation and demonstrate grid-friendly performance under the new readiness-based requirements. It also outlines how well-specified NERs support resilient, predictable operation as demand on infrastructure continues to grow In December 2025, the UK’s National Energy System …<\/p>\n","protected":false},"author":1,"featured_media":31221,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[104,199],"tags":[14402,5758,765,14400,14401],"class_list":["post-31219","post","type-post","status-publish","format-standard","has-post-thumbnail","","category-electronics","category-news-views-and-opinion","tag-connections-reform","tag-cressall-resistors","tag-data-centres","tag-high-resistance-grounding","tag-neutral-earthing-resistors-ners"],"yoast_head":"\nHow high-resistance grounding keeps data centres online - Engineer News Network<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.engineernewsnetwork.com\/blog\/how-high-resistance-grounding-keeps-data-centres-online\/\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"How high-resistance grounding keeps data centres online - Engineer News Network\" \/>\n<meta property=\"og:description\" content=\"Mike Torbitt explores how neutral earthing resistors enable data centres to treat first earth faults as alarm-only events, maintain continuous operation and demonstrate grid-friendly performance under the new readiness-based requirements. 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