Safety When working on or near Electrical installation

By: Suresh S

12 July 2024 at 10:28

Section1 - Welcome and Introduction

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

Section2 - Legal Foundataions:

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

Voltage levels:

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 Accident prevention regulation DGUV, regulation1, 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".

The Regulations in Germany

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

Technical Rules in Germany

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.

DGUV Regulation1 - Principles of prevention
DGUV Regulation3 - Electrical installation and equipment
DIN VDE 0105-100 "Operation of electrical installations" (This contains European minimum requirements + additional extensions

Other Rules:

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

The overall Regulations in Europe:
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)

Section 3 - The Dangers of Electricity

Biggest threats of electricity

Electric Shock
Injuries from instinctive reaction to an electrical shock
Burns due to an explosion or an arc flash/arc blast

Electrical Shock:

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 arc flash.

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

The current path
The touch voltage
The duration of the current flow
The frequency
The degree of moisture of the Skin
The surface area of contact
The pressure exerted and temperature

Basic overview

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.

Path of the current:

Impact of touch voltage:

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

Area of contact:

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.

Frequency

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,

Perecption threshold - < 0.5mA
Reaction threshold - < 0.5mA
Release threshold - < 5mA
Ventricular fibrillation & unconsciousness thresholds - >30-40mA

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

< 0.5mA can be tolerated for long time. Slight tingling can be felt
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
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
500mA to 10000mA - life threatening area. Cardiac arrest/Ventricular fibrillation, hyperinflation of lungs, burns and other injuries

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

Possible fall/an unstable platform
Injuries due to sharp edges
Loss of tools/equipment
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

Section 4: Basic Principles of Electrical Safety

Levels of Responsibility:

The person responsible for electrical safety - Employer/Owner
- Overall responsibility of safe operation
- Establish the rules and organization framework
The nominated person in control of an electrical installation during work activities - Professional with high level of electrical knowledge.
- Responsible for safe operation of electrical installation of work activities
- Professionally qualified to access how work must be carried
- Higher electrical qualification than the electrician.
The nominated person in control of the work activity - Foreman of work
- Responsible for the safety of all individuals involved including people that are near to electrical installation
- Tasked to oversee all activities
- Ensure the operations are performed according to safety regulation.

Skill levels:

Low --> Ordinary person
Medium --> Instructed person (EuP)
High --> Skilled person (EFK)

Safe operation & Risk Assessment:

Safe Operation:
Basic rule is to ensure safe opertion. Therefore prior to work activity, risk assessment must take place

This evaluation must identify hazards if any and call for appropriate safety measures and precautions for safety of workers and equipment

Risk Assessment
Before work, all should agree on tasks to be done and necessary precautions. What may happen?

flow of current through the body
Short circuit with direct or indirect consequences

Risk Assessment process

Personnel:

Competence requirement:

Requirements for Personal Protective equipment
Instruction requirements
Habits and Behavior at work

Organization
Responsibility of electrical installation

Basically this is the owner
or CEO of company
when owner unable to provide risk assessment, person with sufficient qualification must be called in.

Delegation of responsibility
Two or more installation and/or Entrepreneurs
The access to Electrical hazardous areas

Access control
Sign board

Competence of skilled person

Communication
Communication can be passed orally or by written and using any communication devices in a clear and reliable manner

The work location
Site preparation

Adequate working space
Access
Lighting

Non electrical hazards - Precaution
Flammable materials - To be kept away

Tool, equipment and devices
Drawing, Records and Signs
Emergency arrangements

Review questions:

Section 5: Operational Procedures

(Operating Activities, Measurement, Testing and Inspection)

This section deals with the requirements of DIN VDE 0105-100 regarding the operation of electrical installations
This includes switching operations, functional Tests/Measurements, testing and inspection

General:
When working near or on electrical installation, you must use appropriate tools and equipment to protect against Hazards.

Before the work is started, it must be approved by

The person responsible for electrical installation or
The nominated person in control of the electrical installation during work activities

After the completion of work, it must be informed to

The person responsible for electrical installation or
The nominated person in control of the electrical installation during work activities.

Operating Activities
Operating activities are designed to change the electrical state of an electrical installation

This is divided into

Daily use operations intended to modify electrical state without risks (Connect/Disconnect, Start/Stop)
- Skilled or instruction person are allowed
Safety operation intended to disconnect or reconnect the installation incase of work on or near electrical installation
- Skilled(EFK) or instructed(EuP) person only allowed to do this

Functional checks, Measurement

Functional checks and measurment can be performed only by EuP or EFK
Ordinary persons are only allowed to carry out under the supervision of Skilled person(EFK)
Skilled person must learn what? How? Where? what to measure?
Slightest doubt, nominated person in conrl of the electrical installation during work activities must be contacted.

Safe Instrucments

Only approved, permitted tools must be used when working on electrical installation. Instruments should comply DIN EN61010-1 (VDE 0411-1).

Risk of accidents due to Measurments must be taken into consideration.
Internal resistance of a meter must be taken care.

Whenever there is a risk of direct contact with uninsulated live parts, PPE to protect against electric shock, short circuits or arcs must be used.
As long as the installation is classified as fully IP2X or better, wearing rubber gloves or appl insulating covers is not mandatory

Testing Qualifications

Testing includes to check the operation of electrial, mechanical or thermal condition of installation.
It also include measurment activities accordance with the regulations measurement. only EuP or EFK allowed to carry out this.

Dead State Testing:

Inspections

It may include

Visual examination
Measuring and/or testing in accordance with the requirements of measurments and tests

This must be carried out with regard to the current electrical drawings and specifications.

Skilled person with experience in inspection are allowed to carry out. This is carried out to protect the personnel from hazards, considering the constraints imposed by the presence of bare live parts.

Results of inspection must be recorded as per national and local law. If necessary appropriate remedial action shall be taken.

Recurring inspection

Periodic inspection is required
It can be for random samples.
Scope and results of the periodic inspection of an installation shall be recorded in an inspection reports.

Review:

Section 6 Working Procedures General Aspects

This section describes the general rules that must be observed in the specific work methods for dead working, live working and working in the vicinity of live parts.

This section is divided into three parts

General Requirements
Requirements incase of induced voltages
Requirements in case of weather conditions

Safe operation Risk assessment:

Responsibility and Authority:

Only the nominated person in control of the electrical installation during work activities is authorized to issue or withdraw a permit of the planned work

Working Methods

There are three different working methods

Dead working
Live working
Working in the vicinity of live parts

Regardless of methods above, protection against shock, short cicuit and arcing must be taken

Specific requirements if risk of induction

Specific requirements incase of weather condition

Unfavorable environment conditions may cause limitations to the commencement of continuation of work. Example are

Lightning
Heavy rain
Thick fog
Strong winds

In case of weather related interruptions, nominated person in control of the electrical installation during work activities must be informed.

Insufficient visibility condition, no work should be started and all work activities in progress must be stopped after securing the work location.

Review:

Section 7: Dead working Procedure

In order to avoid electrical hazards, comply with Five safety rules. Prior to starting up work the following must be identified and understood

The workplace
the electrical system
the associated sources of danger and hazards.

The five safety rules:

When the five safety rules are carried out by an instructed person, the person must be given the following instructions in detail

What must be disconnected?
How must the installations be secured against reconnection?
On which precise circuits and terminals must the absence of voltage be measured/Determined?
How and on which component must the earthing clamps be mounted?
Which live parts need to be covered, how should they be covered, and possible other actions to ensure protection against accidental contact?

Review

Section 8: Live Working

Here we cover live working: That is any work that is performed on liveparts or inside the live working zone of installation.

Definition:
All work in which a worker deliberately makes contact with live parts or reaches into the live working zone with either parts of his body or with tools, equipments or devices being handled

Introduction:

Low voltage - work is considered as live working when getting in direct contact with live parts
High voltage - All work in live working zone must be treated as live work, regardless of whether there is contact with liveparts or not.
Live working involves an increased risk of Short circuiting and electric shock. With proper safety rules adherence, work can be performed without incidents
Comparted to dead working zone, there is greater likelihood of an incident occuring when working live
Highest priority must therefore beto comply with all safety regulations.
Dead working or working in the vicinity of live parts is perferred working method.

The decision to work live cannot be made by the employee alone. Your company as well as your customer must be involved. Hopefully they will not want to take the risk associated with live working. The follwing risks are,

Injuries to personnel
Damages to equipment
Electric arcs, explosions and
Downtime nd rebuilding

Regulations:

Live working must be carried out in accordance with national regulations.
National regulations or additions apply prior to European standard DIN EN 501110. In Germany DIN VDE 0105-100:2015 as well as the DGUV regulations (German social accident insurance) apply before the Eurepean Standard.

Safety precautions

Check the national requirements first.
DIN EN 50110-2 National annexes contains snapshot of the regulations of the different countries at the time when the annexus were edited.
risk assessment must be peformed
All type of possible hazards must be identified and evaluated in relation to probability and severity Eg:
1. THe voltage level
2. The short circuit energy
3. The insulation level of the installation
4. The nature of the work and the work site

Voltage level

Short circuit level

Low voltage installations:
Identifying and evaluating the electrical hazards of the electrical installation in essential prior to live work.

Resp: Person responsiblie for the EI during work activities.

Electrical installation can be divided into

Extra low voltage
Low voltage without dangerous short circut current.
Low voltage with dangerous short circut current.

Extra low voltage installations:
When SELV installations, work can be carried out without protection against direct contact with live parts. However precautions must be taken to protect against short circuit.

Low voltage installations:()incl FELV & PELV
For installations protected against short cirucits, overload, the below requirements apply

insulation of adjacent live parts
Use of insulated tools
Use of appropriate PPE

Low voltage with dangerous SC current:
Small short circuit (<2kA) may be dangerous. Neither DIN VDE 0105-100 nor DIN EN 50110-1 describe whe SC is dangerous. The requirement is

THe risk of short cirucuit must be calculated according to DIN EN 61482, NFPA 70E or IEEE 1584

Decision process:

No1:

No2:

No3:

6.3.1:

6.3.2 Specific Training and Qualification

Special training must be setup. The training must include
1. Theoretical exercise
2. Practical exercise These exercise must be tailored to the work to be done after training.
Table 5 of DGUV regulation 3 has list of live work allowed

The person responsible for the installatin during work activities must confirm the level and ablity to perform live work with certificate of competence.

Certificate example:

6.3.3 Maintaining personal skills for live working
The ability to carry out live work safely must be maintained
. An ongoing practical routine
. A new training
. A refersher training

The person responsible for the installation during work activities assess all certificates atleast anually.

DIN VDE 0105-100 recommends repeating the thery and practical instruction for every four years.

Also skill, health checks, qualification of employees must be checked.

6.3.4 Working methods

6.3.5 Working conditions

6.3.6 Tools, equipments and devices

6.3.7 Environmental conditions

6.3.8 Organization of work

Section 9: Working in the vicinity of live installations

Live working zone and the vicinity zone

The zones at low voltage:

The zones at high voltage:

Definition of working in the vicinity of live parts:

General aspects:

Preventing access to the work location:

Section 10: Maintanance Procedures

General:

Personnel:

Maintanance - Planned and approved by the nominated person in control of electrical installation during work activities
when doing maintanance on or near to electrical installation, the following points must be clearly defined
- The relevant part of installation to be worked
- The person responsible for maintenance often nominated person in control of work activity

  1. must be a skilled or instructed person

  2. must be qualified to perform the work

  3. appropriate tools and measurement equipment and PPE must be used

Repair work
It consists of following stages