EHAZOP – Electrical HAZOP / ELSOR – Electrical Safety and Operability Review 

Objective

The objective of the Electrical System Hazard and Operability Study (E-HAZOP) study is to identify all hazard and operability issues associated with the electrical network. High voltage distribution system will be covered in this review while the main electrical generation shall be considered for interface issues only. In case of multiple identical electrical systems, only one system will be analysed whereas the study results will be applicable to all identical systems.

The detailed objectives include:

• Identify the reaction of plant and equipment systems to electrical perturbations and deviations;
• Assess whether the reaction of the system, or plant or equipment will produce effects which are detrimental to the public, personnel, environment, asset protection and business continuity policy of the Company;
• Investigate the operability of the electrical network;
• Identify system robustness and reliability issues such as single point failures, common cause failures, etc;
• Recommend corrective actions which will mitigate or eliminate such detrimental effects, or request further investigation to identify suitable actions

E-HAZOP Methodology

Overview

The study will be performed on single line diagrams (SLDs) available at the time of E-HAZOP review. The study will also refer to equipment specifications, layouts and other documentation listed in the later section.

Methodology

Words to generate a set of Deviation from design intent. The Causes and Consequences of each deviation are identified. Safeguards that can prevent or mitigate the hazard, and which are already provided in the design, are listed. Additional safeguards if required to mitigate the hazard will be considered by the team and listed as Recommendations for consideration by the design team or the project team.

The facilitator (Team Leader) will ensure that the technique is systematically applied to all parts of a system such that safety and operability problems on the complete system are identified.

Collection and use of information

The relevant information and data will be made available to the study team as early as practicable prior to the commencement of the study for familiarising purposes.

Review document to be made available to the team during the sessions:

• Single line diagrams (required): this refers to the electrical distribution
• Equipment room layout
• Typical electrical installation details (cabinets, etc.)
• Normal and essential load list
• Earthing and lightning philosophy
• Black start/ load shedding requirements (interfaces with main PGU contractor)
• Overall cable routing layouts
• Description of ESD/ F&G interfaces with electrical system (or ESD cause and effects)
• Typical electrical protections and (if available) metering diagrams

Reference document to be made available during the sessions:

• Design philosophies
• Process description, PFDs, PIDs, C&E diagrams should be available for reference
• Site overall layout
• Hazard area classification list
• Equipment list and data sheets (if available)
• Equipment room fire protection philosophy and systems
• Process description, PFDs, PIDs, C&E diagrams should be available for reference
• Lighting layouts if available
• selectivity/harmonics study (if available)
• Team members should familiarise themselves with the information and circumstances of the project and prepare notes on any important issues which should be raised.
• At the beginning of the session relating to an electrical sub-system, as well as at the beginning of each node, a presentation will be made by the electrical engineer from the design team/project team to explain the system

General Review of System

This task consists of a general discussion aiming at gaining familiarisation with the following:

• Electrical system;
• Design standards;
• Company specifications;
• Electrical distribution configuration;
• Load sharing/load shedding/black start (interfaces with main “Utility & Offsite” contractor);
• Security of supplies;
• Electrical room environment, fire protection and layout;
• Switching and interlock philosophy;
• Maintenance and sparing philosophy; and
• Cable routing/location of electrical substations etc.

The results from this discussion will form the basis for the E-HAZOP

Nodes

The facilities will be broken down into a number of sub-systems based on the system design and its complexity. The electrical sub-system will be sectionalised into manageable discussion nodes based on the facilitator’s experience and input from the team. Study nodes will be, for instance, power generators, main electrical switchboard, sub-stations, fire suppression system, emergency/ uninterruptable power supply, load shedding system, etc.

A reference number will be given to identify the selected node. The team will identify the intention of the node and operability limits will be recorded.

Guide Words

The E-HAZOP study will be carried out in a systematic and methodical manner on all the nodes using a step-by-step approach and the application of guide words to the system under study.

All applicable deviations will be examined by combining appropriate guidewords to process or other parameters.

Consequences

The potential consequences of each deviation will be discussed and assessed within the limits of the information available and the expertise of the team. The potential consequence will be assessed focusing on possible major effects in terms of operability, personal safety and electrical supply reliability.

For each consequence, a severity ranking shall be done as follows:

Safeguards in place

The team will identify safeguards that are effective in preventing or controlling the problems identified. Only safeguards that are independent of the initial cause of the deviation are considered.

E-HAZOP recommendations

The team will provide recommendations if the existing protective measures are considered to be inadequate by the team. Actions will be recommended to eliminate or mitigate any residual hazard that is considered significant.

The recommendation may take the form of design changes, operation / maintenance philosophy or request for further clarification on design basis