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The e-HAZOP: Taming the risks of electrical systems

Engineering the safe generation, transmission, distribution and use of electricity is a specialised discipline. The intricate behaviour of electricity at both micro and macro scales, coupled with its capacity to cause serious harm, is a major challenge for power system designers and operators.

Growth in low carbon power generation and storage, as well as the electrification of energy consumption, are accelerating the demand for effective electrical engineering. This rapid pace of change amplifies technical challenges for those connecting new power systems into established and increasingly complex power networks.

The electrical HAZOP, or e-HAZOP, is a proven technique that can play a key role in enabling the safe grid integration of net zero technologies.


A Hazard and Operability study (HAZOP) is a systematic risk assessment of a process or system.  It is commonplace in sectors like chemical, oil and gas. The study is typically conducted in a multi-disciplinary workshop and uses guidewords to help identify hazards and operability issues associated with a specific process or system. The approach is organised around the international standard for HAZOP studies, IEC 61882.

An e-HAZOP focusses on electrical systems. The workshop is attended by electrical system designers, constructors, and operators. For a power generation or storage asset the study is often structured to “follow the electron” – that is, from the grid connection down to the asset, or vice-versa, using busbar voltage levels as nodes.  The nodes are marked up on electrical system drawings and the team also draws upon other information such as single line diagrams and electrical studies.

The study applies electricity specific guidewords as prompts to systematically identify and assess the potential hazards.  The primary tool for recording the output of the study is the hazard register, which facilitates the assessment of each hazard and associated mitigations to eliminate or reduce risk.


An e-HAZOP would typically be run when the design has progressed to a sufficient level of detail to interrogate.  This may be at pre-consent concept design or, certainly, during Front-End-Engineering-Design (FEED). The core objective of the study is for the design to reduce the residual risk to those personnel who will be operating and maintaining the facility to ALARP levels (As Low As Reasonably Practicable).

Like traditional process HAZOPs, e-HAZOPs are often re-run as the project design becomes more detailed and journeys through its lifecycle. For example, it is often beneficial to run several e-HAZOPs on the same system at different times, such as prior to commissioning and periodically during operations.

The energisation of electrical plant and equipment presents particular risk when equipment is energised for the first time outside of the factory, for example transformer inrush or first-time switching operations. Dedicating an e-HAZOP to commissioning activities and their sequencing is particularly worthwhile for complex facilities.

An operational e-HAZOP is beneficial when a significant modification to the system design is required, such as additional mandated equipment to comply with grid code requirements.  Furthermore, an e-HAZOP can be re-run after a set interval, for example five years, to revalidate the system by considering the accumulation of all minor equipment and operating changes, as well as the gained operational experience.


A significant advantage is that the e-HAZOP is a systems level study. It does not look at electrical equipment in isolation, but in the broader context of the whole power system. This involves assessing the integration of all electrical plant and equipment including generators, transformers, switchgear, cabling, protection and earthing.

A systems approach is crucial because a facility’s electrical equipment is interconnected, both with itself and the wider electrical grid network. The risk of a localised fault causing safety issues on other nearby equipment is significant. But the ripples of the fault can also be felt beyond and into the wider network (and potentially vice-versa), creating asset and commercial risk due to enforced disconnection by grid operators.


Electricity by nature is hazardous and complex. It is crucial that those involved in e-HAZOPs have a thorough theoretical as well as practical understanding of electrical engineering.

Electrical engineering has its own technical language. It is vital for competent people to be present who have a thorough understanding of electricity’s behaviour in electrical power systems. This ensures electrical hazards and risks are identified and recorded accurately and efficiently; a general engineer may miss counterintuitive hazards and operability issues.

As a straightforward example, LOTO is a frequently used term which is perhaps not fully appreciated by the non-electrical engineer. LOTO stands for ‘lockout/tagout’ and is a protective procedural control that involves a lock as a physical barrier and a tag with hazard messaging.  It aims to prevent the release of hazardous electrical energy from isolated electrical power sources.

LOTO is the practical means by which operations and maintenance on electrical equipment is authorised and safely facilitated.  It makes sure that electrical plant and equipment is inoperable, shutdown or de-energised where relevant. In some geographies LOTO is specifically mandated by law.  As a result, e-HAZOP attendees must include those with operational experience of power systems including procedures such as LOTO.

energy storage


Whilst the laws of physics that govern the behaviour of electricity have not changed, the application of electricity is rapidly advancing. Innovative technologies supporting the energy transition bring opportunity but also new challenges.

For example, dynamic cables for floating offshore windfarms might be anticipated to fail more frequently during their operational life compared to a fixed foundation. How will dynamic cables be repaired safely offshore with risk reduced ALARP? Will it be feasible to have floating offshore substations with several inter-array dynamic cables as well as export cables in close proximity?  And be able to conduct repairs to each of them safely and in a way that minimises asset downtime?

The e-HAZOP is the ideal tool for identifying and enabling the management of such potential hazards and operability issues for complex and innovative systems.


Managing the electrical hazard has always been challenging.  The pioneer Nikola Tesla wrote in 1896 that “electricity has been a great blessing to mankind, but it has also proved a new source of danger” (Ref. 1). Whilst the electrical hazard’s nature may not have changed, mankind’s controlled and applied use of electricity continues to change due to technological advances and societal demand.

The complex challenge of the energy transition magnifies the need for ‘electrifying’ safety tools and techniques such as e-HAZOPs, to enable the safe pursuit and delivery of widespread clean electrical power.


  1. Stevens Point Daily Journal, Stevens Point, Wisconsin, 20th July 1896.


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