{"id":7656,"date":"2024-07-17T02:00:41","date_gmt":"2024-07-17T01:00:41","guid":{"rendered":"https:\/\/www.viperinnovations.com\/?p=7656"},"modified":"2026-02-17T15:09:25","modified_gmt":"2026-02-17T15:09:25","slug":"five-facts-about-insulation-resistance-testing","status":"publish","type":"post","link":"https:\/\/viper-innovations.webboxdemo.co.uk\/us\/news\/five-facts-about-insulation-resistance-testing\/","title":{"rendered":"A Simple Guide to Insulation Resistance"},"content":{"rendered":"

Insulation resistance (IR)<\/strong> is how well an insulator can prevent current flowing between two conductors or flowing to ground. In the context of subsea engineering, insulation resistance generally refers to the electrical integrity of the umbilical cable that runs from the topside to the subsea control equipment. If the insulation resistance is low enough, the signals cannot run through the cables and the electrical system will stop working. <\/span>\u00a0<\/span><\/p>\n

As insulation resistance can degrade gradually, regular testing is important for the safety and reliability of electrical systems, to prevent costly umbilical failure, and to protect against electrical shocks.\u00a0 <\/span><\/p>\n

Watch the video to learn more about Insulation Resistance<\/strong><\/p>\n

What is insulation resistance?<\/span><\/h3>\n

Insulation Resistance <\/span>is the ability of the insulation material to prevent leakage currents flowing between live conductors, or from the conductors to ground. When the <\/span>insulation resistance is high, the integrity of the cable is good. However, if the insulation resistance breaks down, it can eventually cause electrical failure of the subsea equipment and lost production.<\/span><\/p>\n

In subsea applications, equipment downtime and replacement of umbilicals or the Electrical Flying Leads (EFLs) between equipment will inevitably be expensive. It is crucial that testing and monitoring is carried out. Insulation degradation tends to occur over time, so having complete and continuous information allows developing issues to be monitored, mitigated against, and resolved quickly.<\/span><\/p>\n

What are the causes of low insulation resistance?<\/span>\u00a0<\/span><\/h3>\n

Understanding the causes of low insulation resistance is crucial for maintaining system reliability and performance. Low insulation resistance can become problematic as insulation ages, and several factors can accelerate this degradation. These factors are typically categorised as either intrinsic or extrinsic.<\/p>\n

Intrinsic factors<\/strong> are faults native to the system, such as those that occur during manufacture or assembly, incorrect design or material quality issues.<\/span><\/p>\n

Extrinsic factors<\/strong> include mechanical stress of the cable or connectors during installation or handling. This can damage the insulation, as can collision damage from vessel anchors or ROVs. Scouring damage from the seabed is also a known source of degradation.\u00a0<\/span>\u00a0<\/span><\/p>\n

As insulation deteriorates, it can develop cracks or holes, allowing moisture and other contaminants to infiltrate. This intrusion lowers the insulation’s resistance, worsening over time and potentially leading to significant performance issues.<\/p>\n

Watch the video to understand the potential consequences of operating a subsea electrical system with low Insulation Resistance (IR).<\/strong><\/p>\n

What is insulation resistance testing?<\/h3>\n

Insulation resistance testing<\/strong> checks insulation resistance integrity. <\/span>The <\/span>theory behind insulation resistance testing<\/span><\/a> is derived from Ohm\u2019s Law \u2013 apply a known voltage between conductors and earth before measuring the leakage current drawn. A figure can then be calculated, with the result expressed in Ohms (\u03a9).<\/span>\u00a0<\/span><\/p>\n

Continuous monitoring with an insulation resistance test machine, such as an insulation\u00a0<\/span>monitoring device (IMD), will typically use an AC waveform because DC measurements are susceptible to interference from noise or stray currents.<\/span>\u00a0<\/span><\/p>\n

Read more on the theory of insulation resistance testing<\/a><\/span><\/p>\n

How to test insulation resistance<\/strong><\/h4>\n

There are two ways to test insulation resistance. These are:\u00a0\u00a0<\/span>\u00a0<\/span><\/p>\n

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  1. Installing a <\/span>Line Insulation Monitor<\/span><\/a> (LIM) allows continuous surveillance of the system while in service. Automatic alarms can be generated if the insulation resistance parameters exceed predefined limits, especially useful when integrated with a SCADA system. LIMs typically apply a low frequency AC voltage.<\/span>\u00a0<\/span><\/li>\n
  2. Periodic or on-demand testing can also be carried out on an energised system using an insulation resistance tester that applies a high DC voltage for a set period. The results can be interpreted to identify the approximate nature as well as the presence of a fault.<\/span>\u00a0<\/span><\/li>\n<\/ol>\n

    What are the types of Insulation Resistance Testing?<\/h3>\n

    There are <\/span>different types of <\/span>insulation resistance testing <\/span><\/a>namely; spot reading test, time resistance test, polarisation index test and step voltage test.\u00a0<\/span><\/p>\n