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DeadEasy FAQs
This page provides some frequently asked questions and answers on DeadEasy.
Why do I need to test that an isolation switch / circuit breaker is "off" once I have turned it off?
Mainly because electrical isolations even if the correct switch is turned off and locked, are not always sound.
We generally think that once we have turned off and locked an isolating switch or circuit breaker that the equipment is 100% safe to access. Not so, many, many switches from the largest manufacturers have failed in a mode that allows switches to pass current in the "off" position. The switch failures have caused fatalities in Australia and in the USA. The fatalities have motivated Australian legislation towards the need to verify isolations. This legislation now requires confirmation or verification. Many tests have been developed to test isolating switches. Some tests that are used today are cumbersome and some are potentially misleading. |
What switch failures have occurred?
Switch failure modes that allow the passing of current in the off position include:
- Welded switch contacts.
- Worn handles that fail to rotate the switch mechanism when the handle is rotated.
- Misaligned handles that fail to engage with the “handle to switch” connecting shaft.
- Switch bypass faults – cable-to-cable faults.
Perhaps there is a message in the fact that all major manufacturer's of isolating switches now incorporate Visible Break Isolators (VBI) in their range!
What is so special about DeadEasy?
DeadEasy was designed to:
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Provide non-electrical people with a simple and safe method of verifying MCC (Motor Control Centre) based, electrical isolations before conducting mechanical maintenance.
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Provide operator confidence in the reported test result through the use of a operator initiated, self test function.
- Be implemented in new and retrofit applications by being inexpensive to purchase and simple to install.
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Provide minimal impact on the integrity of the power system to which it is connected.
What is the difference between SwitChek and DeadEasy?
SwitChek provides greater testing flexibility than DeadEasy as it can conduct a test whether or not the line side of the switch is alive or dead. This is important for field isolators as the line side of the switch is most likely to be deenergised at the time of testing. DeadEasy requires the line side of the switch to be alive at the time of testing. As such it is most suitable for switchboard or motor control centre verification of isolation.
Can I really rely on a non-contact method when testing for dead?
DeadEasy measures the electric field that is generated by a live AC conductor. All live AC conductors generate this field. When the source generating the field is referenced to earth eg via an MEN link, the field also seeks a path to earth through DeadEasy. Other devices that use this principle to determine whether a conductor is live or dead include non-contact test pencils and high voltage live line indicators.
Non-contact test pencils have not always had a good reputation. This seems to be due to the poor integrity of the earth connection provided by the operator. That is, PPE such as gloves and work boots may impede the operator's path to earth and prevent the detection of a live conductor. Where the connection to earth is sound, the approach is regarded as safe and as such forms the basis of most high voltage test for dead, testing. This technique is enhanced if self testing is employed as in the case of DeadEasy.
One problem that may exist with non contact capacitive methods is the reporting of deenergised conductors as energised. Whilst this is a “fail to safety” result it could not be tolerated if the result was repeatedly incorrect. As a result, Redbusbar recommends that the DeadEasy should only be installed on circuits which are not exposed to noise when the circuit under test is deenergised. Therefore DeadEasy should be installed on circuits that are of short length and that are confined to within an MCC (Motor Control Centre) cell. A typical DOL drive cell where DeadEasy is installed between a circuit breaker and a contactor would therefore be a suitable location. Of course the following circuit conditions are also likely to provide staisfactory operation, we just can't guarantee it:
- Power circuits in steel wire armoured cables
- Where local isolators are immediately adjacent to motors and the motor cables under test are not run in the proximity of other circuits
- Where a load impedance with respect to earth is connected to the circuit under test. For instance a SwitChek 33 Interface could be used as the load impedance
In the remainder of cases where high levels of ambient electric fields exist, DC injection test methods such as Meggering and SwitChek represent the better alternatives.
Could I simply get an electrician to check the isolation?
Manual Isolation Testing using a high voltage test set (Megger) to report the fact that there is no passage, via the cabling in the circuit under test, between the line side and load side of the isolating switch. It tests both the switch and the connected cabling. However, if the line side of the switch is alive the person performing the test is at risk. In most cases the Megger is simply not rated to protect the person performing the test. Informed companies have recognised this exposure and test using a multimeter instead. Of course mutimeters do not generate a typical service voltage so they do not stress test the switch.
Wouldn't it be cheaper to just get an electrician to verify the isolation?
Yes, but only if you perform less than 1 isolation every 3 months on an individual isolator. In this case the cost of purchasing and installing DeadEasy is more expensive than paying for an electrician to manually confirm an isolation. This cost comparison is quite conservative. What's not included are the costs associated with maintenance/construction team waiting for the electrician to arrive. In addition, the cost assessment is based on the first year's costs. Of course in the second and subsequent years DeadEasy costs are negligible whilst manual confirmation of isolation costs are ongoing.
In summary, if you perform 1 isolation every 3 months on an individual isolator, DeadEasy payback is one year. Of course the cost assessment does not highlight which method of isolation confirmation is technically superior!
Could I simply use an Attempt a Start method to verify the isolation?
The “Attempt a Start” isolation procedure aims to determine, through the use of local or remote starting methods, that the isolation switch prevents the motor from starting. This is useful in allowing non-electricians to determine whether it is safe to perform mechanical maintenance on a motor e.g. grease bearings. The procedure for the “Attempt a Start” method is largely dictated by the facilities avalable for isolation and motor control and their locations.
The disadvantages of this approach are as follows:
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In most circumstnces the “Attempt a Start” method used does not actually stress test the isolation switch. In fact, it tends to prove that the control circuit is inhibited in someway eg emergency stop operated, incorrect mode (local/remote). The problem with this is is that it is the isolation switch that is locked. This means that later correct operation of the control circuit could reveal a faulty isolation switch with dangerous consequences.
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The “Attempt a Start” method often contains between 8 and 16 steps. Some of our clients believe that it is unrealistic to expect operational personnel to perform this procedure or even to perform it correctly on each and every occasion. In essence, they feel that a judge would see it this way also in the event of an accident.
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The procedure can be complex and it changes from plant to plant which makes it necessary to conduct special and regular training.
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The “Attempt a Start” method maybe inconvenient to use due to control interlocks. That is, several other items may be required to start before starting the equipment of interest. Because of this arrangement confirming the isolation is sometimes abandoned.
Could I simply install pilot lamp, phase indication on the load side of the isolation point?
This approach has been trialed before by our clients and generally takes the form of fixed pilot lamps that can be read by a non electrician. The thinking being that prior to initiating the isolation all lamps are illuminated and after performing the isolation all lamps are extinguished. This result is taken as being a confirmed isolation.
The disadvantages of this approach are as follows:
- Poor pilot lamp to neutral connections yield shock voltages on the isolated side of a healthy switch. This point alone is reason enough not to pursue pilot lamps as it leads to potential electric shock situations.
- Using a strict testing approach, which is what is required when confirming an isolation, the approach to achieving a high integrity test result involves testing the lamps, testing the switch, testing the lamps = confirmed result. Clearly, when using pilot lamps, the last "testing the lamps" step can not be conducted without reversing the isolation or installing costly self-test circuitry. This defeats the purpose of the isolation in the first place! This scenario demonstrates how a blown lamp could yield an incorrect confirmation of isolation result.
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Lamps regularly fail due to vibration. Operating a switch handle causes significant transient vibration.
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Short lamp life when used on variable speed drive (VSD, VVVF) or soft starter circuits. Harmonic currents use the lamps as a path to earth which leads to failures within weeks.
- If the line side of the isolation point is dead, phase indication as a means of confirming an isolation cannot be performed.
If you need more convincing download a copy of the "Confirming Electrical Isolations" white paper on the DeadEasy page.
Could I simply install visible break isolators (VBIs) as the isolation point?
Visible Break Isolators (VBI) report the fact the isolating switch is open. However, they are large, expensive and disruptive to prdouction when installing. Given the fact that they also provide no protective function they really do not provide a viable solution for MCC (Motor Control Centre) applications.
How can I install additional wiring to the load side of our circuit breakers, which are our isolation points, if we have close coupled contactor or overload units?
If you decide that proof of isolation is important to you and your company, you realistically have a choice of:
- Manual Testing.
- Visual Break Isolators.
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DeadEasy.
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SwitChek.
If you also decide that manual testing is too dangerous or cumbersome then either Visual Break Isolators, DeadEasy and SwitChek require some modifications to your MCC (Motor Control Centre). Most switchgear manufacturers sell separate mounting kits for their contactors and Thermal Over Loads (TOLs).
How can I install small gauge DeadEasy wiring onto large power circuit cabling?
DeadEasy does not electrically connect to the conductive parts of the power circuit. Therefore, it does not affect the performance of the power circuit in response to power system voltage disturbances. DeadEasy senses the electric field surrounding the energised power conductor without actually contacting the live parts.
Do you know how expensive it would be to make provision for DeadEasy testing on every switch we have?
We know that DeadEasy will be expensive to implement on every switch. However, if you decide that proof of isolation is important to you and your company, manual testing and Visible Break Isolator (VBI) approaches are generally more expensive.
Our suggestion is that you start by identifying the isolation switches in your plant that present the most risk to personnel. That is, the switches that:
- Are used to frequently isolate plant for maintenance, cleaning or inspection access, and switches that ....
- Isolate equipment that people climb into or major portions of their body are inserted into. That is, it has the potential to seriously injure or kill.
Start with providing a solution for these equipment items first. Alternatively, you risk becoming overwhelmed by the task at hand and doing nothing!
What sort of equipment do you suggest that we should implement DeadEasy on?
Whilst it has been a Legal requirement in Queensland, Australia since 1994 to confirm isolations on all equipment, the following equipment generally exposes the personnel to greater access (hence exposure to severe injury or death) when being maintained:
- Printing Press.
- Jaw Crusher.
- Wood Chipper.
- Cut-off Saw.
- Conveyor.
- Forging Machine.
- Ball Mill.
- Ribbon Blender.
Who else makes a MCC (Motor Control Centre) based, Self Testing, Test for Dead isolation point tester?
To our knowledge, no one! DeadEasy is Patented.
Will testing present a hazard to persons working on upstream or downstream equipment?
No. The opearator initiated, self test, test voltage applies less than 1V to the power conductors.
Will additional switchboard penetrations compromise the fault containment performance of our switchboard?
Potentially, yes but not likely. This would need to be considered for your installation. The DeadEasy Human Machine Interface (HMI) penetration is approximately 25mm in diameter. This penetration is required to fit 1 x 22.5 pilot indicator light. This is certainly a better arrangement than multiple pilot lights or a window for a Visible Break Isolator (VBI).
How can I be confident that DeadEasy is going to report accurately?
DeadEasy has undergone rigorous laboratory and field testing. Just as manual testing derrives its accurate result from the user following a strict, 3 step, testing procedure, so too does DeadEasy. However, DeadEasy provides the operator with the controls and indications to simply and safely perform the testing procedure.
A failure modes and effects analysis (FMEA) conducted on DeadEasy indicated that a single fault within the test system will not impede the safety function and will be detected and indicated to the user. What this means is that DeadEasy will have a long life span typical of all electronic equipment. However, if it should fail it will indicate that the test is invalid because of the failure and that the operator will not be placed at any risk. It will not indicate a deenergised state when in fact the circuit is energised.
If you are familiar with IEC 61508 the following information maybe of benefit:
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Proof Test Interval (Years) |
PFD average |
Safety Integrity Level (SIL) |
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0.5 |
7.51 x 10^-4 |
2 |
|
1.0 |
1.50 x 10^-3 |
2 |
|
2.0 |
3.0 x 10^-3 |
2 |
λtotal = 976.10 x 10^-9
λsafe = 804.55 x 10^-9
λdangerous = 171.55 x 10^-9
SFF = 82%
Does that mean that if I install DeadEasy I don't need need to Test for Dead before performing electrical maintenance?
No. In fact, testing for dead is a legal requiremnet in most jurisdictions. There are however good reasons why you should not rely on it to verify an isolation in some cases.
If you need more convincing download a copy of the "Confirming Electrical Isolations" white paper on the DeadEasy page.
Does DeadEasy reduce the risk of our people being exposed to an Arc Flash?
It sure does! One of the best approaches to reduce the risk of arc flash is to remove power. In the past this meant turning the switch off and perhaps viewing phase indication lights. This approach to proving dead introduces the possibility for error. Switch contacts don't always separate and you can never really be sure why the phase indication light is not illuminated. Is the light or fuse supplying the light blown, has the LED failed due to harmonic currents from a VVVF drive, has a wire dropped off? DeadEasy provides a true indication that power within the MCC drive cell has been removed prior to the door being opened. This may go someway to reduce the level of PPE required to open the MCC cell door. In essence the main risk has been removed.
Arc Flash risk reduction is just another benefit of the DeadEasy, Test for Dead, Test Device.
Is there a money back policy?
DeadEasy will not report a deenergised state when in fact the circuit is energised. Should DeadEasy fail to satisfy this requirement you will be refunded in full! Including all freight costs!
Under these circumstances Redbusbar reserves the right to inspect the installation and witness the incorrect operation of DeadEasy. In addition, damage to or deliberate tampering of DeadEasy shall waive this policy.
Who can operate DeadEasy?
Anyone. If you can touch the Human Machine Interface (HMI) to activate the self test and read an indication light you can operate DeadEasy. No licenses are necessary.
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