Safety When working on or near Electrical installation
Published: 2024-07-12 10:28:52

## **<u>Section1 - Welcome and Introduction</u>**
- This course provides basic information to perform safely when working on or near electrical installations

- This is based on German and European regulations and standards including DGUV regulation, DIN VDE 0105-100, EN 50110-1 and other relevant standards

## **<u>Section2 - Legal Foundataions:</u>**

Here the standards and rules to be considered <u>when working on or near electrical installations</u>. Concepts of European standard and application in Germany will be discussed in simple terms.

<u>Voltage levels:</u>
- 0-1000V AC
- 0-1500V DC

Safely working is important and information about correct and safe approach must be provided to the workers. Hence this course is important. Also according to <u>Accident prevention regulation DGUV, regulation1</u>, Employers duty is to provide safety instructions to all individuals once a year. This will give a cap and can be appointed as **electro technically instructed person**. Main Objective is "to ensure maximum safety to all individuals".

**<u>The Regulations in Germany</u>**
- How to act safely when <u>working on or near electrical installations or equipment based on DGUV regulation 3 and DIN VDE 0105-100</u> is covered here. This is specific to Germany. 
- European standard for <u>Operation of electrical installations EN50110 </u>imposes less strict requirements

**<u>Technical Rules in Germany</u>**
- There are techinical rules for workplaces and operational safety
- Accident insurance agencies **BG ETEM (for the electrical industry and electrical work)** issue accident prevention regulation together with **DGUV**

The following rules are important.
1. **DGUV Regulation1** - Principles of prevention
2. **DGUV Regulation3** - Electrical installation and equipment
3. **DIN VDE 0105-100** "Operation of electrical installations" (This contains European minimum requirements + additional extensions

Other Rules:
1. DIN VDE 0100 - Low voltage electrical installations
2. DIN VDE 1000-10 . Reqs for persons working in a filed of electrical engineering.





**<u>The overall Regulations in Europe:</u>**
European Standard for Electrical safety regulation is published by **CENELEC**. EN50110-1 is **"Operation of electrical installations**
- Part1:
Minimum requirements for safety performing electrical work and applied to all CENELEC members
- Part2: Set of annexes, one per each country.

EN50110 can be applied everywhere. Many countries outside Europe thinks this is enough as long as it is not work on liveparts or HV (>1000V AC/1500V DC)

## **<u>Section 3 - The Dangers of Electricity</u>**
Biggest threats of electricity
1. Electric Shock
2. Injuries from instinctive reaction to an electrical shock
3. Burns due to an explosion or an arc flash/arc blast

<u>**Electrical Shock:**</u>

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/sk6l4n386vn6iuev05cz.png)

The damage to the part depends on **Duration** and **amount of energy** running through it. Greater amount of energy & greater duration, greater the damage.
 - Effect * Duration = Energy
 - P(W) * h (hours) = E (kWh); 1kWh is 3.6megajoule (MJ)

Consequence of current through the body can be very low(harmless) to Very high(fatal) for an almost similar situations. The current through the circuit can be calculated using Ohms law.
- **U(v)=R(ohm)*I(A)**
- **I = U/R**

**Voltage:**
Here magnitude of voltage is crucial for the current. So higher the voltage, **the greater and more dangerous the current becomes**. In high voltages, even without touching the live parts, a circuit can be made via air through an <u>arc flash</u>.

**Internal Impedance of Human body:**
Once the person becomes part of electrical circuit, impedance of human body determines the consequence. The standard **DIN IEC/TS 60 479-1** refers to the effect of electrical current on human beings. The value of body impedance depend on several factors
1. The current path
2. The touch voltage
3. The duration of the current flow
4. The frequency
5. The degree of moisture of the Skin
6. The surface area of contact
7. The pressure exerted and temperature

**<u>Basic overview</u>**
- In DC installation, circuit has a certain **Resistance** 
- In Ac installation, the correct term of resistance is **Impedance**

When talking of AC, the impedance(Z) is the product of Resistance(R), the inductive resitance(XL) and the capacitive resitance (Xc)

In Human bodies, body impedance may vary for person to person. At 400V AC 50/60 Hz, hand to hand current path, dry condition and large contact area, the average impedance is **950ohms**. 5% of people it will be **700ohm or less**. 5% of people it will be **1275ohms or more**.

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/72l3lxk5rb4qq23aekbc.png)

<u>Path of the current:</u>
![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/dlfl1bzp4wj3l1c80ebc.png)

<u>Impact of touch voltage:</u>
![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/n79v0f0j18utv31g955y.png)

<u>Humidity:</u>
Moisture reduces the impedance incase of electrical contact. So wet hands leads to more impact of electrical current flow.

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/5c4tr27cqoleq6jxyrpp.png)

<u>Area of contact:</u>
- Large contact surface of 10000 mm2 (10x10cm) - low impedance
- Medium contact surface 1000 mm2 (3.1x3.1cm) - Medium  impedance
- Small contact surface 100 mm2 (1x1cm) - high impedance

If we use ohmmeter with probe, body impedance from hand to hand, the value will be between **100,000 to 2000 000 Ohms**. This is due to Skins high impedance. It decreases quickly once a current flows through. Without Skin the impedance of the body is much lower. More info: DIN IEC TS 60479 -1.

<u>Frequency</u>

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/20tq3sdctrcnu7co0uo9.png)

**The Amount of Energy:**
According to the standard DIN IEC TS 60479 -1, 


> The current  and duration of current flow through the body is decisive for injuries. Current depends on voltage and Impedance of circuit. Time depends on whether the installation disconnects automatically.(Circuit breakers are slow in reaction but RCD interrupt the circuit at max 300ms)

The amount of energy is calculated
- **I2(Current) * Time = Energy**

As the current is the indicator of electrical shock, the effects can be,
1. Perecption threshold - < 0.5mA
2. Reaction threshold - < 0.5mA
3. Release threshold - < 5mA
4. Ventricular fibrillation & unconsciousness thresholds - >30-40mA

**Effects of Current on Human beings and livestock:**
As per IEC,

1. < 0.5mA can be tolerated for long time. Slight tingling can be felt
2. 0.5mA to 200mA - Increase in BP, muscle spasms and involuntary muscle reactions
  - Upto 5mA can be tolerated for long time
  - 30 mA approximately 200ms
  - Upto 200mA duration less than 10ms
3. 200mA to 500mA - Strong muscle reactions, difficulty in breathing, distruption of the heart rhythm. Furthermore as it is above release threshold, unable to let go off the power source due to lack of muscle control

4. 500mA to 10000mA - life threatening area. Cardiac arrest/Ventricular fibrillation, hyperinflation of lungs, burns and other injuries

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/r8edd1a6krdrs7kal6lm.png)

Secondary effects is injuries that occur after an electrical shock. For example Fell of a ladder after shock leads to Broken bones.
Aware of following

1. Possible fall/an unstable platform
2. Injuries due to sharp edges
3. Loss of tools/equipment
4. Head injuries

Short circuit:
European standard describes electrical arc flash as rare events. But when this occurs, the consequences are severe. This may occur because of loss of tools, malfunction of electrical devices and etc. So wear arc protection cloths and take protective measures against arcs.

Railway overhead lines in germany operated at 15kV. Safe distance is 3m.
Electrical accident example is shown of loosing multiple fingers. The person is an electrician and have performed the work several times. As he did not follow the rules, it leads to fatal damage. 1 or 1million in Germany. 1 of 1.1million in US



## **<u>Section 4: Basic Principles of Electrical Safety</u>**