People who carry out work on or near electrical equipment must consider certain key elements to promote safe working practices and take all the necessary precautions for health and safety. Jack is quite determined to grill Lucy because itʼs such a vital subject for their trade.
Jack: So, Lucy, what did you learn about safety rules this morning?
Lucy: Oh, nothing I could tell you in just a few sentences. Itʼs quite a comprehensive subject. I never would have expected this much.
Jack: It should be quite obvious, however, considering that electricity can easily become a danger to life and limb. Moreover, a danger foreseen is half avoided.
Lucy: Well, there are two main hazards – thermal and shock. When electric energy is converted to thermal energy faster than it can be safely dissipated, this will lead to undesired heating effects. Take a short circuit, for example, caused by worn through insulation of two wires and thus allowing them to come into contact. As the resistance of the short, r, is very small, the power dissipated in the short, P = V2/r, is very large.
Jack: Letʼs assume V is 120V and r is 0.100Ω. How much power would this be?
Lucy: Well, that must be 144kW, which is definitely too high for a common household appliance. This thermal energy will raise the temperature of surrounding materials, melting or even igniting them. Intense heat can also be generated by electrical arcing, perhaps resulting from a short circuit. This in turn can cause deep-seated and slow-healing burns or even damage to the eyes.
Jack: Bravo! What about other hazards?
Lucy: The other ones are shock hazards. By the way, they can also be used for positive side effects when electrical current passes through people.
Jack: That sounds quite amazing, in fact.
Lucy: You bet! Electrical current can be used to block back pain or to stimulate muscle action in paralyzed limbs. Or it can help against ventricular fibrillation.
Jack: Youʼre talking in riddles now, my dear.
Lucy: Well, thatʼs when you suffer from a massively irregular beating of the heart, which is often fatal. In this case, a heart attack victim can be saved by electrical shocks. Or think of a pacemaker that stimulates the heart to beat properly by electrical shocks.
Jack: I see what you mean, but common electricians are more confronted with shocks ranging from painful but harmless to heart-stopping lethality. It depends on the amount of current, the path taken by it, the duration of the shock and the frequency of the current.
Lucy: Yes, of course. Most electrical fatalities occur because a current put the heart into fibrillation. In many cases, muscular contractions are caused with the victim being thrown back when the shock passes through the trunk of the body and the legs, for example. It could be that the victim canʼt let go of the wire stimulating the muscles in the hand.
Jack: Are you sure, you donʼt want to work in the medical field with all these exhaustive details you remember? Just kidding. Itʼs very important to be aware of these dangers at all times. Risk assessment is indispensable to identify hazards in the workplace and to consequently evaluate the risks to avoid that any harm will occur. So, letʼs discuss some precautions you need to take in advance.
Lucy: Alrighty! Recognizing electrical wires is crucial, no matter whether theyʼre overhead powerlines, electrical wiring in a house or cables buried in the ground. Moreover, working away from electrical wiring whenever possible, or if not possible, turning off the electrical supply and making sure it is off and that nobody can turn it on again without permission is just as important. When there are still electrical live circuits, danger notices should be put up. Even if there are none, cables may still be nearby, so itʼs a good thing to always stay vigilant.
Jack: How exactly do you ensure safe isolation to prevent conductors and equipment from inadvertently being energized?
Lucy: Apart from using the main switch or distribution board switch connector and locking it off, we should use devices for proving that conductors are dead. This could be a test lamp or a two-pole voltage tester which, of course, must also be proved to be working on a known live source or a proprietary proving unit. All line, neutral and protective conductors should be tested to prove theyʼre dead.
Jack: Can you think of a situation where it would make sense to permit live working?
Lucy: Yes, there are some exceptions to dead working. When itʼs completely unreasonable for the conductor to be dead and reasonable at the same time for the person working on or near the conductor while itʼs live, provided that all the necessary precautions have been taken, of course.
Jack: What do you mean by unreasonable?
Lucy: Well, it could be difficult or even impossible to put a complex control cabinet into operation without energizing it at some stage with parts live. Or how would you monitor the operation and performance of a control system or do the fault-finding? Another reason could be if too many customers had to be disconnected from a distribution network or if excessive disruption and cost were involved when carrying out maintenance or repair work on an electric railway track, for example. Needless to say, all this is only possible if very strict safety rules and procedures to prevent injury can be applied.
Jack: Very well-explained, young lady! You can tell from all this that safety is a full-time job.
Lucy: Yes, indeed. Be careful with power, or this will be your last hour!
In my last article, you learned something about the use of reflexive pronouns (mich, dich, sich, uns, euch)
I often ask myself this question. Ich stelle mir oft selbst diese Frage.
Iʼve cut myself. Ich habe mich geschnitten.
Subject and object are the same person.
These are some common reflexive verbs in English, which means you always need ʻmyself, yourself, herself, himself, ourselves, yourselves or themselvesʼ together with the verb:
to enjoy oneself: sich amüsieren
I enjoyed myself very much at the party last night.
to hurt/injure oneself: sich verletzen
He fell off his bike and hurt himself.
to introduce oneself: sich vorstellen
May I introduce myself, Iʼm your new supervisor.
to make oneself something: sich etwas selbst zubereiten
I made myself a cup of coffee.
There are some verbs, however, which are used as reflexive verbs in German but not in English (so no ʻmyself, yourselfʼ etc. is used with them):
to apologize: sich entschuldigen I apologized because I was late.
to change: sich (ver)ändern New York has changed a lot.
to complain: sich beschweren He complained about the food.
to decide: sich entscheiden She decided to quit her job.
to imagine: sich etw. vorstellen Can you imagine being a millionaire?
to look forward to: sich freuen auf I look forward to my next holiday.
to meet: sich treffen They met with some friends in town.
to relax: sich ausruhen/entspannen We all relaxed on the beach.
to remember: sich erinnern I canʼt remember what I had for lunch yesterday.
to sit down: sich setzen He sat down on a seat near the door.
to worry: sich Sorgen machen Donʼt worry, be happy!
Quiz: Choose the correct version:
- Last Monday I got up at six, then I
a) showered myself b) showered.
- She really
a) feels well today b) feels herself well today.
a) meet us b) meet ourselves c) meet at six tomorrow.
- Yesterday Jack cooked dinner and
a) burnt himself b) burnt him c) burnt.
- May I introduce
a) me b) myself.
- You can
a) sit b) sit you c) sit yourself on the chair over there if you wish.
a) concentrate yourself b) concentrate while doing your homework.
- I was so scared, I could hardly
a) move b) move myself.
- She often
a) remembers the trip to Australia b) remembers herself of the trip to Australia.
- We can't
a) imagine b) imagine ourselves living without electricity.
1b, 2a, 3c, 4a, 5b, 6a, 7b, 8a, 9a, 10a
So much for today. I hope you had some fun with this little quiz.
After so much electrical safety information, Lucy is very eager now to really get some electrical hands-on tasks at the construction site. Letʼs see and stay tuned!