Electrical LV Testing Safely

Chris Halliday presented this paper at the 2022 Mines Electrical Safety Conference in Brisbane. You can watch the presentation or read the paper following:

Much of the risk associated with LV testing can be designed out but this won’t happen overnight due to budgeting issues and the actual time to achieve risk elimination or reduction. In this paper, some guidance will be provided on how to manage the risk in the short term and what controls should be implemented in the longer term.

Setting the Scene

To set the scene for this paper, the implications for the victim and the company if things go wrong will be discussed.

The victim may be extremely lucky, and no untoward effects caused by getting testing wrong. A ‘tingle’ may be received with no real effects, or a fall from the ‘tingle’ could cause a death or severe injury.

You may have already heard of Mark; he was connecting a power quality logger when an arc was established. He suffered severe injuries and had to have extensive rehabilitation to overcome his physical injuries.

Long-term psychological injuries may also result. Implications can also include the loss of employment and livelihood. There can also be flow on effects such as the stress placed on loved ones and friends. Death can also occur from electrocution or arc flash injuries.

The implications for the company or business include:

  • Investigators, supervisors and co-workers may be adversely affected. There may be significant stress for all involved that may spill over into personal life
  • Grieving relatives and friends will need to be advised, counselled and/or consoled.
  • There is likely to be downtime that may affect production.
  • Loss of reputation may affect the interaction with other businesses.
  • Damage to branding is linked to loss of reputation.
  • There will be reporting, and additional paperwork and we all love paperwork.
  • There will be additional costs associated with the ensuing investigation.
  • Rectification costs to prevent reoccurrences.
  • Legal defence fees and court appearances.
  • Worker’s compensation premiums are likely to increase.
  • Loss of licenses could be an additional outcome.
  • For some businesses, it could result in their ultimate demise and loss of livelihood.
  • Company, personal fines and imprisonment could result from prosecution by the safety regulator (see Figure 1).
  • Where a PCBU, or senior officer, is found to have committed industrial manslaughter, a maximum penalty of 20 years imprisonment for an individual, or $10,000,000 for a body corporate applies in QLD.

Types of and Issues with LV Testing

There are specific laws applicable to the mining industry including requirements around testing in explosive areas.

The Queensland Electrical Safety Regulation 2013, which has more general application, has specific requirements for LV testing. These requirements include:

A person conducting a business or undertaking (PCBU) has a duty to manage risks to health and safety associated with electrical risks in Section 11.

Section 14 specifically prohibits electrical work on energised electrical equipment.

Section 15 requires electrical equipment to be tested by a competent person and that is treated as ‘live’ until isolated and found not to be ‘live’. In the case of high voltage (HV) it must also be earthed.

Section 17 has requirements for Lock Out/Tag Out (LOTO).

Whilst Section 14 prohibits electrical work on energised electrical equipment, Section 18 allows work in very specific circumstances such as:

  • It is in the interests of health and safety for the electrical equipment to remain ‘live’ e.g. life saving equipment must stay energised.
  • It is necessary that the electrical equipment to be worked on is energised in order for the work to be carried out properly.
  • Testing de-energised as required by Section 15.
  • Lastly, there is no reasonable alternative to ‘live’ work.

Section 19 to 22 provides requirements that could be classed as control measures if ‘live’ work must be carried out. This includes that the person authorises the live’ electrical work after consultation with the person with management or control of workplace.

‘Live’ testing includes:

  • Testing for ‘dead’ as already mentioned to comply with the regulation.
  • Fault finding.
  • Monitoring and testing.
  • Compliance and functional testing to meet the requirements of the mandatory tests from the Wiring Rules and the ‘test and tag’ standard AS/NZS 3760.

Each of these will be discussed in more detail with a focus on the short and longer term controls.

Daniel connecting a non-contact power quality logger on double insulated cables.

Testing ‘Dead’ Control Measures

Testing ‘dead’ is regarded as ‘live’ work under the Regulation and so standard or safe work procedures and PPE will be needed. Full arc flash PPE may be required as detailed via an arc flash study or from AS/NZS 4836.

Non-contact testers/proximity testers can be used initially to minimise the arc flash risk. Fused voltage leads with retractable probe covers will also be useful. Please note, the risk with arc flash has only been minimised from the initial use of contact meters and not from issues such as accidental operator contact.

Up to date plans will also help to prevent issues and keeping plans up to date is a legal requirement in mining.

In the longer term, absence of voltage testers can eliminate the risk. Various makes and models are available including an Australian version. These will be needed at the source of the electricity supply for each final sub-circuit, and at the electrical equipment supplied by the final sub-circuit.

Fault Finding Control Measures

Fault finding control measures for the short-term include de-energised testing first. Such tests are usually continuity tests and insulation resistance tests. Insulation resistance tests also generate voltages that can cause incidents and so must be carefully managed.

Where de-energised testing fails to find the cause of the issue, the exemption “Necessary that the electrical equipment to be worked on is energised in order for the work to be carried out properly” under Section 18 of the Regulation could be used but the arc flash and electrocution risks must be managed. Compliance with Section 19 to 22 of the Regulation is required and the use of suitable PPE and detailed procedures for the work will be needed.

In the longer term, options to minimise the risks include the use of extra low voltage control circuits, up to date plans as previously mentioned, settings for protective devices that reduce the available energy and the replacement of protective devices with faster settings and with monitoring capability.

Regular and targeted maintenance will reduce the number of faults. Condition monitoring can also be used to identify maintenance issues as faults are developing but condition monitoring needs to be such that it doesn’t introduce additional risks (more on this to come).

Monitoring Control Measures

General monitoring and testing, say tonging cables to check loads or taking a voltage reading, doesn’t fit with the exemptions for prohibited ‘live’ work. The monitoring/test equipment will therefore need to be connected with the supply isolated, ‘livened’ for the test, then de-energised and the test instrument disconnected. This process will need to be detailed in procedures and the operating/switching risk managed.

Longer term, various permanently installed monitoring options can be used. These include low incident energy test blocks, circuit breakers with monitoring capability, and permanently installed monitors with remote communication.

Compliance/Functional Testing Control Measures

The sequence of mandatory tests is as per AS/NZS 3000. Polarity can be tested with continuity testers as provided by AS/NZS 3017 but should be tested once supply is available – non-contact proximity testers will minimise the risk.

RCDs and RCBOs poles can be verified by continuity tests and not voltage tests. RCDs and RCBOs functional tests can be performed by a simple push button test if switched socket outlets aren’t available.

Of course, all compliance and functional testing will need a procedure (and training in the procedure).

Longer term, test devices for RCD and RCBO compliance and functional tests can be installed that eliminate the risk.

Functional and Compliance Testing Standards

Condition Monitoring

Condition monitoring, such as thermal imaging, can be quite dangerous and whilst a ‘bomb’ suit might manage the incident energy, do you really want a person exposed to that level of risk with a low order control?

Longer term, options for condition monitoring include using crystal windows for portable thermal imaging cameras or the installation of fixed cameras or fixed mounted cameras with a panning option. Alternatively, temperature sensors can be used to monitor critical equipment and busbars and acoustic monitors can also be used to monitor for loose and arcing connections.

De-energised Test with Voltage

Continuity Tests

One make and model of a continuity tester

The output voltage/current from continuity testers is generally below the threshold of perception and so presents an extremely low risk.

Test instruments with a continuity test function should be self-protected against an accidental ‘live’ LV test, particularly multifunction testers.

Insulation Resistance Testing

Insulation resistance testing is reasonably safe as the available touch current is generally below the threshold of let-go. However, the available touch current is above the threshold of reaction and may therefore cause severe incidents because of falls, head knocks, etc.

Insultation resistance testers should have a self-discharge function to minimise the risk from contact after tests. Procedures will be needed including the use of testing permits if more than one person is involved at the site.

A commonly used make and model of insulation resistance tester

Obtaining Funds

The risks of testing LV safely can be minimised in the short term, mainly by lower order controls from the hierarchy of controls, longer term higher order controls, such as those previously mentioned, should be implemented to minimise or eliminate the risk.

Testing safety risks should be analysed, perhaps on a companywide or site-by-site basis, and prioritised. Control measures should be costed and a report with an action plan developed based on the risk.

Once the report/plan has been developed, consultation will be needed to gain support and funding for the work. Implement the control measures as funding is made available and working down the list from higher priority risks to lower priorities.

Conclusions

In conclusion, LV testing presents a significant risk that must be managed or injuries and death may result. Failing to adequately manage the risk can have a considerable impact on the company, managers, employees, family and friends.

Companies have legal obligations to manage the risks posed by LV testing. Short term management options are needed but it is best to design out the risk using the latest technologies. Analyse all LV testing risks, prioritise the risks, plan, report, budget and implement.

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