Power supply systems and protective measures · Exercise 5: Customer installation project: handing...
Transcript of Power supply systems and protective measures · Exercise 5: Customer installation project: handing...
WorkbookTP 1111
With CD-ROM
Festo Didactic
567309 en
Power supply systemsand protective measures
RCD
M3
RCD
N
L3
L2
L1
N
PE
L3
L2
L1
M3
PEN
L3
L2
L1
M3
Order no. 567309
Revision level: 10/2012
Authors: Jürgen Stumpp
Edited by: Frank Ebel
Graphics: Remo Jedelhauser, Thomas Ocker, Jürgen Stumpp
Layout: 10/2012, Susanne Durz, Frank Ebel
© Festo Didactic GmbH & Co. KG, D-73770 Denkendorf, Germany, 2013
Internet: www.festo-didactic.com
E-mail: [email protected]
The purchaser shall receive a single right of use which is non-exclusive, non-time-limited and limited
geographically to use at the purchaser's site/location as follows.
The purchaser shall be entitled to use the work to train his/her staff at the purchaser's site/location and
shall also be entitled to use parts of the copyright material as the basis for the production of his/her own
training documentation for the training of his/her staff at the purchaser's site/location with
acknowledgement of source and to make copies for this purpose. In the case of schools/technical colleges
and training centres, the right of use shall also include use by school and college students and trainees at
the purchaser's site/location for teaching purposes.
The right of use shall in all cases exclude the right to publish the copyright material or to make this available
for use on intranet, Internet and LMS platforms and databases such as Moodle, which allow access by a
wide variety of users, including those outside of the purchaser's site/location.
Entitlement to other rights relating to reproductions, copies, adaptations, translations, microfilming and
transfer to and storage and processing in electronic systems, no matter whether in whole or in part, shall
require the prior consent of Festo Didactic GmbH & Co. KG.
© Festo Didactic GmbH & Co. KG 567309 III
Table of Contents
Use for intended purpose __________________________________________________________________ IV
Preface ______________________________________________________________________________ V
Introduction ____________________________________________________________________________ VII
Work and safety instructions ______________________________________________________________ VIII
Training package for “Power supply systems and protective measures” (TP 1111) ___________________ IX
Learning objectives ________________________________________________________________________X
Equipment set ___________________________________________________________________________ XI
Notes for the teacher/trainer _______________________________________________________________ XII
Structure of the exercises _________________________________________________________________ XIII
CD-ROM contents ________________________________________________________________________ XIII
Exercises and solutions
Overview of power supply systems ____________________________________________________________ 3
Exercise 1: Measurements at power supply systems ____________________________________________ 5
Overview of protection against electrical shock ________________________________________________ 29
Exercise 2: Protection against electrical shock – protection during normal operation ________________ 31
Exercise 3: Protection against electrical shock – protection in case of fault ________________________ 43
Exercise 4: Protection against electrical shock during normal operation and in case of fault __________ 65
Exercise 5: Customer installation project: handing over a service installation to a customer __________ 71
Exercises and worksheets
Overview of power supply systems ____________________________________________________________ 3
Exercise 1: Measurements at power supply systems ____________________________________________ 5
Overview of protection against electrical shock ________________________________________________ 29
Exercise 2: Protection against electrical shock – protection during normal operation ________________ 31
Exercise 3: Protection against electrical shock – protection in case of fault ________________________ 43
Exercise 4: Protection against electrical shock during normal operation and in case of fault __________ 65
Exercise 5: Customer installation project: handing over a service installation to a customer __________ 71
IV © Festo Didactic GmbH & Co. KG 567309
Use for intended purpose
The training package for “Power supply systems and protective measures” may only be used:
For its intended purpose in teaching and training applications
When its safety functions are in flawless condition
The components included in the training package are designed in accordance with the latest technology as
well as recognised safety rules. However, life and limb of the user and third parties may be endangered, and
the components may be impaired, if they are used incorrectly.
The learning system from Festo Didactic has been developed and produced exclusively for training and
continuing vocational education in the field of automation technology. The training companies and/or
trainers must ensure that all trainees observe the safety instructions described in this workbook.
Festo Didactic hereby excludes any and all liability for damages suffered by trainees, the training company
and/or any third parties, which occur during use of the equipment sets in situations which serve any
purpose other than training and/or vocational education, unless such damages have been caused by Festo
Didactic due to malicious intent or gross negligence.
© Festo Didactic GmbH & Co. KG 567309 V
Preface
Festo Didactic’s training system for automation and technology is geared towards various educational
backgrounds and vocational requirements. The learning system is therefore broken down as follows:
Technology-oriented training packages
Mechatronics and factory automation
Process automation and control technology
Robotino® – training and research with mobile robots
Hybrid learning factories
The technology packages deal with various technologies including pneumatics, electro-pneumatics,
hydraulics, electro-hydraulics, proportional hydraulics, programmable logic controllers, sensor technology,
electrical engineering and electric drives.
The modular design of the training system allows for applications which go above and beyond the
limitations of the individual packages. For example, PLC actuation of pneumatic, hydraulic and electric
drives is possible.
VI © Festo Didactic GmbH & Co. KG 567309
All training packages feature the following elements:
Hardware
Media
Seminars
Hardware
The hardware in the training packages is comprised of industrial components and systems that are specially
designed for training purposes. The components contained in the training packages are specifically
designed and selected for the projects in the accompanying media.
Media
The media provided for the individual topics consist of a mixture of courseware and software. The
courseware includes:
Technical literature and textbooks (standard works for teaching basic knowledge)
Workbooks (practical exercises with supplementary instructions and sample solutions)
Lexicons, manuals and technical books (which provide technical information on groups of topics for
further exploration)
Transparencies and videos (for easy-to-follow, dynamic instruction)
Posters (for presenting information in a clear-cut way)
Within the software, the following programmes are available:
Digital training programmes (learning content specifically designed for virtual training)
Simulation software
Visualisation software
Software for acquiring measurement data
Project engineering and design engineering software
Programming software for programmable logic controllers
The teaching and learning media are available in several languages. They are intended for use in classroom
instruction, but are also suitable for self-study.
Seminars
A wide range of seminars covering the contents of the training packages round off the system for training
and vocational education.
Do you have suggestions or criticism regarding this manual?
If so, send us an e-mail at [email protected].
The authors and Festo Didactic look forward to your comments.
© Festo Didactic GmbH & Co. KG 567309 VII
Introduction
This workbook is part of the training system for automation technology from Festo Didactic GmbH & Co. KG.
The system provides a solid basis for practice oriented training and vocational education. The training
package for “Power supply systems and protective measures” (TP 1111) covers the following topics:
Mains supply
– Power supply systems (TN, TT and IT systems)
– Protective measures in the various types of power supply systems
Service connection
– Components of a service connection system
– Additional designations in the TN system (TN-C, TN-S, TN-C-S)
– Selection of protective measures and protective devices
– Measuring instruments for protective measures
– Planning and performance of initial testing per IEC 60364-6 and
Periodic testing per EN 50110
– Preparation of test reports
Subdistributor
– Dealing with protective measures and measuring instruments
– Planning and performance of initial and periodic testing
– Evaluation of measurement results and preparation of test reports
– Recognising, describing and measuring danger due to faults
– Systematic troubleshooting
The workbook for power supply systems and protective measures covers the issue of the safety of electrical
systems in accordance with IEC in a targeted fashion. Special circumstances and measures for preventing
dangerous satiations are addressed on the basis of realistic situations. Knowledge regarding protection
against direct and indirect contact, protection against electrical shock (also in the event of a fault) and
protection by means of RCD, as well as initial and periodic testing of electrical systems and devices is
imparted in project format for various types of power supply systems (TN-C, TN-CS, TT and IT).
A laboratory workstation equipped with fused mains supply power, two digital multimeters and laboratory
safety cables are prerequisites for setting up and evaluating the circuits.
All of the circuits for the 5 tasks are set up using the TP 1111 equipment set.
VIII © Festo Didactic GmbH & Co. KG 567309
Work and safety instructions
General
Trainees should only work with the circuits under the supervision of a trainer.
Observe specifications included in the technical data for the individual components, and in particular all
safety instructions!
Malfunctions which may impair safety must not be generated in the training environment, and must be
eliminated immediately.
Electrical components
Risk of death in case of interrupted protective earth conductor!
– The protective earth conductor (yellow/green) must never be interrupted, either inside or outside a
device.
– The insulation of the protective earth conductor must never be damaged or removed.
In schools and training facilities, the operation of power supply units must be responsibly monitored by
trained personnel.
Caution!
The capacitors in the device may still carry a charge even after it has been disconnected from all power
sources.
When replacing fuses, use specified fuses only with the correct current rating.
Never switch the power supply unit on immediately after it has been moved from a cold room to a warm
room. Under unfavourable conditions, the condensate which forms as a result may damage the device.
Leave the device switched off until it has reached room temperature.
Use only extra-low voltage (max. 25 V DC) as operating voltage for the control circuits in the various
exercises.
Electrical connections may only be established in the absence of voltage.
Electrical connections may only be interrupted in the absence of voltage.
Use only connecting cables with safety plugs for electrical connections.
Pull the plug only when disconnecting connector cables – never pull the cable.
© Festo Didactic GmbH & Co. KG 567309 IX
Training package for “Power supply systems and protective measures”
(TP 1111)
Training package TP 1111 consists of a multitude of individual training materials. The subject of this portion
of training package TP 1111 is the fundamentals of electrical protective measures.
Important components of TP 1111
EduTrainer® mains supply
EduTrainer® service connection
EduTrainer® subdistributor
Media
The courseware for training package TP 1111 consists of a workbook. The workbook include exercise sheets
for each exercise, the solutions to each individual worksheet and a CD-ROM. A set of ready-to-use exercise
sheets and worksheets is included in each workbook for all of the exercises.
Data sheets for the hardware components are made available along with the training package.
Media
Workbooks Power supply systems and protective measures
Digital training programmes WBT electrical protective measures
Overview of media for training package TP 1111
Available software for use in combination with training package TP 1111 includes the digital training
programme for electrical protective measures. This training programme offers an introduction to the subject
matter of protective measures. The leaner also finds out everything about legal regulations.
The media are offered in several languages. Further training materials can be found in our catalogues and on
the Internet.
X © Festo Didactic GmbH & Co. KG 567309
Learning objectives
Exercise 1: Measurements at power supply systems
You will be familiar with the TN-C system.
You will know how the TN-C system is used in actual practice.
You will be familiar with the TN-C-S system.
You will know how the TN-C-S system is used in actual practice.
You will be familiar with the TT system.
You will know how the TT system is used in actual practice.
You will be familiar with the IT system.
You will know how the IT system is used in actual practice.
You will be familiar with the stipulated protective measures for the individual systems.
Exercise 2: Protection against electrical shock – protection during normal operation
You will be familiar with the term “insulation of active parts”.
You will be familiar with the term “cover or enclosure”.
You will be familiar with the term “protection by obstacle”.
You will be familiar with the term “protection by clearance”.
You will be familiar with the additional protection provided by residual current circuit breakers (RCCBs).
You will be familiar with the various types of RCCB.
Exercise 3: Protection against electrical shock – protection in case of fault
You will be familiar with the term “fault type”.
You will be familiar with the terms “fault resistance” and “fault current path”.
You will be familiar with the terms “fault voltage” and maximum permissible “contact voltage”.
You will be familiar with the term “loop impedance” (loop resistance).
You will be familiar with protection by means of automatic shutdown of supply power in the TN system.
You will be familiar with protection by means of automatic shutdown of supply power in the TT system.
You will be familiar with protection by means of automatic shutdown of supply power in the IT system.
You will be familiar with protection by means of equipotential bonding.
You will be familiar with protection by means of non-conducting locations.
You will be familiar with protection by means of earth-free local equipotential bonding.
You will be familiar with protection by means of electrical separation.
© Festo Didactic GmbH & Co. KG 567309 XI
Exercise 4: Protection against electrical shock during normal operation and in case of fault
You will be familiar with the term “SELV”.
You will be familiar with the layout of a SELV circuit.
You will know how SELV circuits are used in actual practice.
You will be familiar with the term “PELV”.
You will be familiar with the layout of a PELV circuit.
You will know how PELV circuits are used in actual practice.
Exercise5: Customer installation project: handing over a service installation to a customer
You will be familiar with the procedure for testing protective measures in accordance with
IEC 60364-6.
You will be familiar with the procedure for visually inspecting the system.
You will be familiar with the procedure for testing the system.
You will be familiar with hook-up and operation of the utilised measuring instruments.
You will be familiar with the procedures for the individually specified measurements.
You will be familiar with test reports and handover reports for electrical systems.
You will be familiar with troubleshooting and eliminating faults in the CEE outlet circuit.
You will be familiar with troubleshooting and eliminating faults in the earthing contact outlet circuit.
You will be familiar with troubleshooting and eliminating faults in lighting circuits.
Equipment set
The equipment set for “Power supply systems and protective measures” (TP 1111) includes all of the
components which are necessary for mastering the predefined learning objectives. Two digital multimeters
and safety laboratory cables are also required for setting up and evaluating functional circuits.
Equipment set for “Power supply systems and protective measures”, order no. 571824
Component Order no. Quantity
EduTrainer® mains supply 571825 1
EduTrainer® service connection 571826 1
EduTrainer® subdistributor 571827 1
XII © Festo Didactic GmbH & Co. KG 567309
Notes for the teacher/trainer
Learning objectives
The basic learning goal of this workbook is the analysis and evaluation of measurement results obtained
from power supply systems. Electrical protective measures are deduced on the basis of these measurement
results This direct interplay of theory and practice ensures fast progress and long-lasting learning. Concrete,
individual learning objectives are assigned to each exercise.
Required time
The time required for working through the exercises depends on the learner’s previous knowledge of the
subject matter. Roughly 1 to 1½ hours should be scheduled for each exercise.
Equipment set components
The workbook and the equipment set are designed to be used together. All 5 exercises can be completed
using components from one TP 1111 equipment set.
Standards
The following standards apply in this workbook:
EN 60617-2 to EN 60617-8 Graphic symbols for diagrams
EN 81346-2 Industrial systems, installations and equipment and industrial products;
structuring principles and reference designations
IEC 60364-1 Low-voltage electrical installations – Fundamental principles,
(DIN VDE 0100-100) Assessment of general characteristics, definitions
IEC 60346-4-41 Low-voltage electrical installations – Protective measures –
(DIN VDE 0100-410) Protection against electric shock
Identification in the workbook
Solutions and supplements in graphics or diagrams appear in red.
Exception: Information and evaluations regarding current are always in red; information and evaluations
regarding voltage are always in blue.
Identification in the worksheets
Texts which require completion are identified with a grid or grey table cells.
Graphics and diagrams which require completion include a grid.
Solutions
The solutions specified in this workbook result from test measurements. The results of your measurements
may deviate from these.
© Festo Didactic GmbH & Co. KG 567309 XIII
Structure of the exercises
All 5 exercises have the same structure and are broken down into:
Title
Learning objectives
Problem description
Circuit or layout
Project assignment
Work aids
Worksheets
The workbook contains the solutions to each worksheet included in the exercise book.
CD-ROM contents
The workbook is included on the CD-ROM as a PDF file. The CD-ROM also provides you with additional
media.
The CD-ROM contains the following folders:
Images
Product information
Images
Photos and graphics of components and industrial applications are made available. These can be used to
illustrate individual tasks or to supplement project presentations.
Product information
Contains product information from the manufacturers of selected components. The representations and
descriptions of the components in this format are intended to show how they would appear in an industrial
catalogue. Additional information regarding the components is also included.
XIV © Festo Didactic GmbH & Co. KG 567309
© Festo Didactic GmbH & Co. KG 567309 1
Table of Contents
Exercises and solutions
Overview of power supply systems ___________________________________________________________ 3
Exercise 1: Measurements at power supply systems ____________________________________________ 5
Overview of protection against electrical shock ________________________________________________ 29
Exercise 2: Protection against electrical shock – protection during normal operation ________________ 31
Exercise 3: Protection against electrical shock – protection in case of fault ________________________ 43
Exercise 4: Protection against electrical shock during normal operation and in case of fault __________ 65
Exercise 5: Customer installation project: handing over a service installation to a customer __________ 71
2 © Festo Didactic GmbH & Co. KG 567309
© Festo Didactic GmbH & Co. KG 567309 3
Overview of power supply systems
Power supply systems
TT system IT systemTN system
T N C S
1 32
Power supply systems, 1: grounding at the power utility, 2: grounding at the consumer; 3: N and PE conductor at the consumer
RB
PEN
RA
PEN PE
L3
L2
L1
RA
PEN PE
N
L3
L2
L1
First letter
Relationship of the power supply system to
ground
Second letter
Relationship of the frame of the electrical
operating equipment in the electrical
installation to ground
Additional letters
Configuration of the neutral conductor and
the protective conductor
T
Direct connection of a point to ground.
T
Direct connection of the frame to ground,
regardless of any existing grounding of a
point within the power supply system.
S
Protective function which is furnished by
means of a conductor which is isolated
from the neutral conductor or the
grounded phase conductor.
I
Either all active parts isolated from ground,
or a point connected to ground via a high
impedance.
N
Direct electrical connection of the bodies
with the grounded point of the power
supply system.
C
Neutral conductor and protective
conductor functions combined into a single
conductor (PEN conductor).
Meanings of the letters
4 © Festo Didactic GmbH & Co. KG 567309
© Festo Didactic GmbH & Co. KG 567309 5
Exercise 1
Measurements at power supply systems
Learning objectives
After completing this exercise:
You will be familiar with the TN-C system.
You will know how the TN-C system is used in actual practice.
You will be familiar with the TN-C-S system.
You will know how the TN-C-S system is used in actual practice.
You will be familiar with the TT system.
You will know how the TT system is used in actual practice.
You will be familiar with the IT system.
You will know how the IT system is used in actual practice.
You will be familiar with the stipulated protective measures for the individual systems.
Problem description
Various power supply systems need to be examined with suitable measuring instruments.
The various systems can be represented by switching or repatching on a mains connection board.
,
Mains connection board
Exercise 1 – Measurements at power supply systems
6 © Festo Didactic GmbH & Co. KG 567309
1. TN-C system
Project assignments
1. Set up a TN-C system at your mains connection board.
2. Complete the entries in the worksheet so that a TN-C system is created.
3. Measure all possible voltages in the TN-C system with a suitable measuring instrument.
4. Enter the measured values to the table furnished to this end.
5. Evaluate the measured values.
6. When is a TN-C system used in actual practice?
Documentation
Textbooks, table manuals
Operating instructions
Data sheets
Internet
Equipment overview
Quantity Component
1 Mains supply
1 Service connection
1 Suitable measuring instrument (e.g. multimeter)
2 Laboratory safety cables
a) Complete the diagram so that a TN-C system is created.
Designate the individual conductors.
PEN
L3
L2
L1
M3
Exercise 1 – Measurements at power supply systems
© Festo Didactic GmbH & Co. KG 567309 7
b) Measuring circuit layout
GNDPE
L1
L1
L2
L2
L3
L3
N
PE/PEN
N
VCC
PE
L1
L2
L3
N
L1
L2
L3
N
PE/PEN
GND
Probe
GND
L1 L2 L3 N PE
L1 L2 L3 N PE
kWh
20m
1,5Ω 47Ω 470Ω 1kΩ 2,7kΩ
N
PE
L
PE
VCCVCC
4
5
mS
UL= 50
VACmAMΩ
N PE L
battery test
L-NL-PEN-PE
VDCVACkDΩHz
TEST
RCD
RLORE
ZLRISO ΔTIΔ
select
clear
recall
store
ZRZLZS
PSC
UN
IK
UF
REPEFC
IKRE
ZERO
Var
AUTOx1/2x1x5
mA300
180°
500
VOLTS2500
1000
1000
0~ S
memory recall +!
ZERO
MEMORY
TEST
F1
F2
F3
F4
V
1,5Ω
Performing the measurement – measuring voltage and frequency
1. Set the rotary switch to the V position.
2. Use the L (red) and PE (green) sockets for this test.
Use the laboratory safety cables.
• The main display (top) indicates alternating voltage.
• The secondary display (bottom) indicates line frequency.
• Press F1 in order to switch the displayed voltage to L-PE.
• Repatch the laboratory safety cables in order to perform the required measurements.
Exercise 1 – Measurements at power supply systems
8 © Festo Didactic GmbH & Co. KG 567309
c) Measure the voltages in the TN-C system
Attention
You will be working with line voltage while performing the measurements.
Do not switch on until the entire circuit has been completely wired!
Conductors Standard value Measured value
L1 – L2 400 V 398 V
L1 – L3 400 V 398 V
L2 – L3 400 V 396 V
L1 – PEN 230 V 230.8 V
L2 – PEN 230 V 230.8 V
L3 – PEN 230 V 231.2 V
Voltages in the TN-C system
d) Evaluate the measured values.
The measured values correspond with the standard values. Minimal deviations can be traced back to
differing loads within the system.
e) What needs to be observed in actual practice in the case of the TN-C system?
In the TN-C system, a PEN conductor is used which functions simultaneously as protective conductor
(PE) und neutral conductor (N).
In the event that the phase conductors are not uniformly loaded, compensating current flows via the
neutral conductor. As a rule, this results in the presence of a voltage between conductive housings of
operating equipment which are connected to PEN, and ground. In accordance with Ohm’s law, this is
the result of cable resistance and flowing current.
Exercise 1 – Measurements at power supply systems
© Festo Didactic GmbH & Co. KG 567309 9
If the PEN conductor is interrupted in an installation, full voltage to ground, i.e. up to 230 V, is applied
to the conductive housings of the operating equipment downstream from the point at which PEN is
interrupted.
TN-C systems are only permissible with copper conductors with a cross-section of at least
10 square mm, or aluminium conductors with a cross-section of at least 16 square mm. This restriction
was specified in order to reduce the likelihood of a broken PEN conductor to a minimum.
2. TN-C-S system
Project assignments
1. Set up a TN-C-S system at your mains connection board.
2. Complete the entries in the worksheet so that a TN-C-S system is created.
3. Measure all possible voltages in the TN-C-S system with a suitable measuring instrument.
4. Enter the measured values to the table furnished to this end.
5. Evaluate the measured values.
6. When is a TN-C-S system used in actual practice?
Documentation
Textbooks, table manuals
Operating instructions
Data sheets
Internet
Equipment overview
Quantity Component
1 Mains supply
1 Service connection
1 Suitable measuring instrument (e.g. multimeter)
2 Laboratory safety cables
Exercise 1 – Measurements at power supply systems
10 © Festo Didactic GmbH & Co. KG 567309
a) Complete the diagram so that a TN-C-S system is created.
Designate the individual conductors.
N
PE
L3
L2
L1
M3
b) Sketch the fault loop in the event of a fault to frame into the graphic below.
N
PEPEN
L3
L2
L1
RARB
IK
IK
IK
IK
Exercise 1 – Measurements at power supply systems
© Festo Didactic GmbH & Co. KG 567309 11
c) Measuring circuit layout
GNDPE
L1
L1
L2
L2
L3
L3
N
PE/PEN
N
VCC
PE
L1
L2
L3
N
L1
L2
L3
N
PE/PEN
GND
Probe
GND
L1 L2 L3 N PE
L1 L2 L3 N PE
kWh
20m
1,5Ω 47Ω 470Ω 1kΩ 2,7kΩ
N
PE
L
PE
VCCVCC
4
5
UL= 50
V
N PE L
battery test
L-N
Hz
TEST
ZERO
MEMORY
TEST
F1
F2
F3
F4
V
1,5Ω
Performing the measurement – measuring voltage and frequency
1. Set the rotary switch to the V position.
2. Use all sockets for this test (red, blue and green).
Use the laboratory safety cables.
• The main display (top) indicates alternating voltage.
• The secondary display (bottom) indicates line frequency.
• Press F1 in order to switch displayed voltage back and forth amongst L-PE, L-N and N-PE.
• Repatch the laboratory safety cables in order to perform the required measurements.
Exercise 1 – Measurements at power supply systems
12 © Festo Didactic GmbH & Co. KG 567309
d) Measure the voltages in the TN-C-S system
Attention
You will be working with line voltage while performing the measurements.
Do not switch on until the entire circuit has been completely wired!
Conductors Standard value Measured value
L1 – L2 400 V 398 V
L2 – L3 400 V 396 V
L1 – N 230 V 230.8 V
L2 – N 230 V 230.8 V
L3 – N 230 V 231.2 V
L1 – PE 230 V 230.4 V
L2 – PE 230 V 229.8 V
L3 – PE 230 V 231.6 V
Voltages in the TN-C-S system
e) Evaluate the measured values.
Except for minimal deviation, the measured values correspond with the standard values.
Voltage between the phase conductors and neutral conductor N has the same value as between the
phase conductors and protective conductor PE.
These voltage values were expected, because the two conductors are connected upstream from
physical separation into neutral conductor and protective conductor.
Exercise 1 – Measurements at power supply systems
© Festo Didactic GmbH & Co. KG 567309 13
f) What needs to be observed in actual practice in the case of the TN-C-S system?
As of the transformer, the TN-C-S initially has the same layout as the TN-C system. At a given point, no
later than as of the point at which the required minimum cross-section of 10 square mm will be fallen
short of, the PEN conductor is split into neutral conductor and protective conductor. These continue
on separately and may not be brought back together again.
The TN-C-S system is widespread in building applications in Germany. The protective conductor and
the neutral conductor are split in the main distributor inside the building.
The PEN conductor is split into the PE conductor (protective function, green-yellow) and neutral
conductor N (operating current circuit, light blue).
The protective conductor may not be used for any purpose other than implementation of the safety
measure which involves connection of all conductive system components, housings etc. to each other
and to the transformer’s neutral point.
Exercise 1 – Measurements at power supply systems
14 © Festo Didactic GmbH & Co. KG 567309
3. TT system
Project assignments
1. Set up a TT system at your mains connection board.
2. Complete the entries in the worksheet so that a TT system is created.
3. Measure all possible voltages in the TT system with a suitable measuring instrument.
4. Enter the measured values to the table furnished to this end.
5. Evaluate the measured values.
6. When is a TT system used in actual practice?
7. Why are residual current devices (RCDs) mandatorily stipulated in TT systems?
8. Examine the dependence of contact voltage on grounding resistance and fault current.
Documentation
Textbooks, table manuals
Operating instructions
Data sheets
Internet
Equipment overview
Quantity Component
1 Mains supply
1 Service connection
1 Suitable measuring instrument (e.g. multimeter)
2 Laboratory safety cables
Exercise 1 – Measurements at power supply systems
© Festo Didactic GmbH & Co. KG 567309 15
Information
Residual current devices (RCDs) are mandatorily stipulated in TT systems!
N
N
PE
L3
L3
L2
L2
L1
L1
M
RCD RCDRCD
RARARB RA
Connection of consumers via RCDs in the TT system
Exercise 1 – Measurements at power supply systems
16 © Festo Didactic GmbH & Co. KG 567309
a) Complete the diagram so that a TT system is created.
Designate the individual conductors.
RCD RCD
M3
N
L3
L2
L1
b) Measuring circuit layout
GNDPE
L1
L1
L2
L2
L3
L3
N
PE/PEN
N
VCC
PE
L1
L2
L3
N
L1
L2
L3
N
PE/PEN
GND
Probe
GND
L1 L2 L3 N PE
L1 L2 L3 N PE
kWh
20m
1,5Ω 47Ω 470Ω 1kΩ 2,7kΩ
N
PE
L
PE
VCCVCC
4
5
mS
UL= 50
VACmAMΩ
N PE L
battery test
L-NL-PEN-PE
VDCVACkDΩHz
TEST
RCD
RLORE
ZLRISO ΔTIΔ
select
clear
recall
store
ZRZLZS
PSC
UN
IK
UF
REPEFC
IKRE
ZERO
Var
AUTOx1/2x1x5
mA300
180°
500
VOLTS2500
1000
1000
0~ S
memory recall +!
ZERO
MEMORY
TEST
F1
F2
F3
F4
V
1,5Ω
Exercise 1 – Measurements at power supply systems
© Festo Didactic GmbH & Co. KG 567309 17
Performing the measurement – measuring voltage and frequency
1. Set the rotary switch to the V position.
2. Use the L (red) and N (blue) sockets for this test.
Use the laboratory safety cables.
• The main display (top) indicates alternating voltage.
• The secondary display (bottom) indicates line frequency.
• Press F1 in order to switch displayed voltage back and forth amongst L-PE, L-N and N-PE.
• Repatch the laboratory safety cables in order to perform the required measurements.
c) Measure the voltages in the TT system
Attention
You will be working with line voltage while performing the measurements.
Do not switch on until the entire circuit has been completely wired!
Conductors Standard value Measured value
L1 – L2 400 V 399 V
L2 – L3 400 V 398 V
L3 – L1 400 V 401 V
L1 – N 230 V 230.5 V
L2 – N 230 V 229 V
L3 – N 230 V 230.8 V
Voltages in the TT system
Exercise 1 – Measurements at power supply systems
18 © Festo Didactic GmbH & Co. KG 567309
d) Evaluate the measured values.
Except for minimal deviation, the measured values correspond with the standard values.
e) What needs to be observed in actual practice in the case of the TT system?
The use of the TT system in combination with residual current circuit-breakers is stipulated, for
example in agricultural and horticultural applications, as well as for distributors at construction sites.
The TT system is also stipulated for portable distributor systems, for example for temporary structures
such as fair ground vehicles.
f) Why are residual current devices (RCDs) mandatorily stipulated in TT systems?
The earth electrode’s grounding resistance must be small enough that maximum permissible contact
voltage is not exceeded and the overcurrent protection device is tripped in the event of a fault.
If fuses or circuit breakers are used, this results in small grounding resistance values which cannot be
achieved economically at nominal current values of greater than 6 A.
If the RCD has a nominal fault current of 30 mA and maximum permissible contact voltage is 50 V,
grounding resistance may amount to 1665 .
If maximum permissible contact voltage is cut in half to 25 V, grounding resistance is also cut in half to
832 .
L A A U R I
Solved for RA
LA
A
U
RI
UL= maximum permissible contact voltage
RA= grounding resistance
IA= nominal fault current of the RCD
Exercise 1 – Measurements at power supply systems
© Festo Didactic GmbH & Co. KG 567309 19
g) Fault current is shown in the following table as measured for various grounding resistance values.
Use these values to calculate the respective contact voltages.
Grounding resistance Fault current Contact voltage
1 k 0.21 A 210 V
400 0.48 A 192 V
200 0.82 A 164 V
100 1.42 A 142 V
40 2.15 A 86 V
20 2.5 A 50 V
h) Evaluate the individual values.
The smaller the grounding resistance, the greater the fault current. If fault current is increased, contact
voltage rises as well in accordance with Ohm’s law. If fault resistance is neglected, contact voltages
occur which exceed the maximum permissible value.
On the basis of contact voltage, grounding resistance would have to be less than 20 . Earthing
resistance values which should be less than 20 are difficult to achieve in actual practice with
individual earth electrodes.
With a maximum permissible contact voltage of 25 V, the required grounding resistance value is
nearly impossible to achieve with individual earth electrodes. RCDs are used in order to fulfil
shutdown conditions in the event of a fault.
Consequently, RCDs are used where specified grounding resistance values cannot be achieved.
Exercise 1 – Measurements at power supply systems
20 © Festo Didactic GmbH & Co. KG 567309
4. IT system
Project assignments
1. Complete the entries in the worksheet so that an IT system is created.
2. Set up an IT system with the help of the mains connection board and the IT board.
3. Measure all possible voltages in the IT system with a multimeter, and enter the values to the table
provided for this purpose.
4. Evaluate the measured values.
5. The transformer in the IT board is designated Dyn5. Explain this designation.
6. Explain when and where the IT system is used in actual practice.
7. Why are insulation monitoring devices (IMDs) mandatorily stipulated in IT systems?
8. Describe the insulation monitoring function.
9. Start up the IT system. Set the IMD to a threshold value of approximately 60 k. Generate an earth fault
with the potentiometer (500 k) and select various resistance values at the ohmmeter (500 k,
200 k, 100 k, 50 k). Describe the reaction of the IMD.
10. Two RCDs (30 mA and 300 mA) are used for shutting down the IT system.
Supplement the IT system with the two RCD boards. Simulate an earth fault from L to PE at the 300 mA
RCD via the potentiometer (500 k) (first fault). Reset the acoustic signal and simulate an earth fault
from L2 to PE downstream from the 30 mA RCD (second fault). Explain how the IT system reacts.
11. Which tasks have to be completed when testing the IT system in accordance with IEC?
Documentation
Textbooks, table manuals
Operating instructions
Data sheets
Internet
Equipment overview
Quantity Component
1 Mains supply
1 IT system
1 RCD board (300 mA, 30 mA)
1 Suitable measuring instrument (e.g. multimeter)
2 Laboratory safety cables
Exercise 1 – Measurements at power supply systems
© Festo Didactic GmbH & Co. KG 567309 21
Attention
There is no connection between active conductors and grounded parts in the IT system.
The bodies included in the electrical system are grounded.
Insulation monitoring devices (IMDs) are mandatorily stipulated in IT systems.
a) Complete the entries in the worksheet so that an IT system is created. Designate the individual
conductors.
Z < RCD
N
L1
L2
L3
RA RARA
M3
Z: impedance
Exercise 1 – Measurements at power supply systems
22 © Festo Didactic GmbH & Co. KG 567309
b) Set up an IT system with the help of the mains connection board and the IT board.
GNDPE
L1
L1
L2
L2
L3
L3
N
PE/PEN
N
VCC
1,5Ω
PE
L1
L2
L3
N
L1
L2
L3
GNDGND
10k�
500k�
1,5�
1,5�
1,5�
1,5�
VCC VCC
L3L2L1N
5 4
+
ONTest
Reset
AL
RAL
mS
UL= 50
VACmAMΩ
N PE L
battery test
L-NL-PEN-PE
VDCVACkDΩHz
TEST
RCD
RLORE
ZLRISO ΔTIΔ
select
clear
recall
store
ZRZLZS
PSC
UN
IK
UF
REPEFC
IKRE
ZERO
Var
AUTOx1/2x1x5
mA300
180°
500
VOLTS2500
1000
1000
0~ S
memory recall +!
ZERO
MEMORY
TEST
F1
F2
F3
F4
V
Performing the measurement – measuring voltage and frequency
1. Set the rotary switch to the V position.
2. Use all sockets for this test (red, blue and green).
Use the laboratory safety cables.
• The main display (top) indicates alternating voltage.
• The secondary display (bottom) indicates line frequency.
• Press F1 in order to switch displayed voltage back and forth amongst L-PE, L-N and N-PE.
• Repatch the laboratory safety cables in order to perform the required measurements.
Exercise 1 – Measurements at power supply systems
© Festo Didactic GmbH & Co. KG 567309 23
c) Measure all possible voltages in the IT system with a multimeter, and enter the values to the table
provided for this purpose.
Attention
You will be working with line voltage while performing the measurements.
Do not switch on until the entire circuit has been completely wired!
Conductors Standard value Measured value
L1 – L2 400 V 410 V
L2 – L3 400 V 410 V
L3 – L1 400 V 410 V
L1 – N 230 V 236 V
L2 – N 230 V 236 V
L3 – N 230 V 236 V
L1 – PE 0 V Not measurable
L2 – PE 0 V Not measurable
L3 – PE 0 V Not measurable
Voltages in the IT system
Exercise 1 – Measurements at power supply systems
24 © Festo Didactic GmbH & Co. KG 567309
d) Evaluate the measured values.
Except for minimal deviation, the measured values correspond with the standard values. The values
are a bit higher, because they were measured while the transformer was overloaded.
A voltage of 400 V prevails between the phase conductors. A voltage of 230 V prevails between the
phase and neutral conductors. These voltages correspond to a 3-phase, 4-wire system.
Due to the fact that all active conductors are isolated from ground in the IT system, there is no
measurable voltage between phase conductor and ground. No point within the IT system may be
directly grounded!
e) The transformer in the IT board is designated Dyn5. Explain this designation.
The designation makes reference to the 3-phase transformer. As is the case with all transformers,
there is a primary winding and a secondary winding.
Letter D: The primary winding is wired in delta connection.
Letter y: The secondary winding is wired in star connection.
Letter n: The neutral conductor is led out at the secondary winding.
Number 5: Primary winding voltage stays ahead of secondary winding voltage by 5 x 30°.
f) Explain when and where the IT system is used in actual practice.
In actual practice, IT systems are only permissible in limited installations with separate transformer or
generator.
IT systems demonstrate single fault security, which significantly increases their reliability. IT system
are used for facilities in intensive care units and operating rooms, in explosion protected areas, in
mining and in smelting plants.
In production facilities, for instance in the chemicals industry, the IT system is used when considerable
economic loss can be expected in the event of a power failure with a TN system.
IT systems are also used by fire departments and disaster control services (generators).
Exercise 1 – Measurements at power supply systems
© Festo Didactic GmbH & Co. KG 567309 25
g) Why are insulation monitoring devices (IMDs) mandatorily stipulated in IT systems?
Due to the fact that no point within the IT system may be directly grounded, no voltage can occur
between phase conductor and ground.
If a fault occurs within the IT system (earth fault), it must be reported immediately and then
eliminated. An insulation monitoring device is used to generate the required message.
A second fault would result in shutdown of the system.
h) Describe the insulation monitoring function.
Insulation monitoring device (IMD)
Insulation resistance in the IT system is continuously monitored by the insulation monitoring function.
The normal operating state (fault-free) is indicated by a green indicator lamp.
The IMD’s threshold value can be adjusted, for example to a value of 50 k. If insulation resistance
falls below the minimum value of 50 k, this state is indicated by means of a yellow lamp and an
acoustic signal. The acoustic signal can be cleared, but optical indication cannot be switched off until
after the fault has been eliminated.
If a second fault occurs, the system is shut down immediately.
Exercise 1 – Measurements at power supply systems
26 © Festo Didactic GmbH & Co. KG 567309
i) Reaction of the IMD
The IT system is started up. A threshold value of 60 k is selected at the IMD. Earth faults are
generated via the potentiometer with different resistance values, and the reaction of the IMD is
observed.
• 500 k: No reaction
• 200 k: No reaction
• 100 k: No reaction
• 50 k: The IMD indicates the fault both optically and acoustically.
If the threshold value selected at the IMD is fallen short of, optical and acoustic fault indication
ensues.
j) Reaction of the IT system to fault 1 and fault 2
Two RCDs (30 mA and 300 mA) are used to shut down the system.
Setting at the IMD = 50 k. An earth fault is simulated at the 300 mA RCD (L1 to PE via the
potentiometer – first fault).
The IMD indicates the fault both optically and acoustically.
The 300 mA RCD does not shut the system down.
The acoustic signal is reset and a second fault is simulated at the 30 mA RCD
(L2 to PE – second fault).
The 30 mA RCD shuts the system down, and the 300 mA RCD is still switched on.
Exercise 1 – Measurements at power supply systems
© Festo Didactic GmbH & Co. KG 567309 27
k) Which tasks have to be completed for initial testing of the IT system in accordance with IEC?
1. Visual inspection
General condition of the system, equipotential bonding, cable types, wire identification,
protection class adequate for the system, system documentation available.
2. Visual inspection and testing
Protective conductor connections, main equipotential bonding, auxiliary equipotential bonding.
3. Insulation resistance measurement
Not required for repeat measurement, measurement without IMD
4. Measurement or calculation of leakage current
Leakage current from the conductor, leakage current from the consuming devices, addition of
individual current values.
5. Grounding resistance measurement
6. Measurement or calculation of contact voltage when first fault occurs.
7. Measurement for verification of the protective measure, shut down when second fault occurs.
8. Testing of the IMD and any included RCDs.
9. Evaluation of results
Preparation of documentation.
Note
IEC regulations concerning insulation monitoring:
• IEC 60364-1: Protection against indirect contact with shut-down and indication
• IEC 60364-7-710: Electrical safety in medical locations
Exercise 1 – Measurements at power supply systems
28 © Festo Didactic GmbH & Co. KG 567309
© Festo Didactic GmbH & Co. KG 567309 1
Table of Contents
Exercises and worksheets
Overview of power supply systems ____________________________________________________________ 3
Exercise 1: Measurements at power supply systems ____________________________________________ 5
Overview of protection against electrical shock ________________________________________________ 29
Exercise 2: Protection against electrical shock – protection during normal operation ________________ 31
Exercise 3: Protection against electrical shock – protection in case of fault ________________________ 43
Exercise 4: Protection against electrical shock during normal operation and in case of fault __________ 65
Exercise 5: Customer installation project: handing over a service installation to a customer __________ 71
2 © Festo Didactic GmbH & Co. KG 567309
© Festo Didactic GmbH & Co. KG 567309 3
Overview of power supply systems
Power supply systems
TT system IT systemTN system
T N C S
1 32
Power supply systems, 1: grounding at the power utility, 2: grounding at the consumer; 3: N and PE conductor at the consumer
RB
PEN
RA
PEN PE
L3
L2
L1
RA
PEN PE
N
L3
L2
L1
First letter
Relationship of the power supply system to
ground
Second letter
Relationship of the frame of the electrical
operating equipment in the electrical
installation to ground
Additional letters
Configuration of the neutral conductor and
the protective conductor
T
Direct connection of a point to ground.
T
Direct connection of the frame to ground,
regardless of any existing grounding of a
point within the power supply system.
S
Protective function which is furnished by
means of a conductor which is isolated
from the neutral conductor or the
grounded phase conductor.
I
Either all active parts isolated from ground,
or a point connected to ground via a high
impedance.
N
Direct electrical connection of the bodies
with the grounded point of the power
supply system.
C
Neutral conductor and protective
conductor functions combined into a single
conductor (PEN conductor).
Meanings of the letters
4 © Festo Didactic GmbH & Co. KG 567309
© Festo Didactic GmbH & Co. KG 567309 5
Exercise 1
Measurements at power supply systems
Learning objectives
After completing this exercise:
You will be familiar with the TN-C system.
You will know how the TN-C system is used in actual practice.
You will be familiar with the TN-C-S system.
You will know how the TN-C-S system is used in actual practice.
You will be familiar with the TT system.
You will know how the TT system is used in actual practice.
You will be familiar with the IT system.
You will know how the IT system is used in actual practice.
You will be familiar with the stipulated protective measures for the individual systems.
Problem description
Various power supply systems need to be examined with suitable measuring instruments.
The various systems can be represented by switching or repatching on a mains connection board.
,
Mains connection board
Exercise 1 – Measurements at power supply systems
6 Name: __________________________________ Date: ____________ © Festo Didactic GmbH & Co. KG 567309
1. TN-C system
Project assignments
1. Set up a TN-C system at your mains connection board.
2. Complete the entries in the worksheet so that a TN-C system is created.
3. Measure all possible voltages in the TN-C system with a suitable measuring instrument.
4. Enter the measured values to the table furnished to this end.
5. Evaluate the measured values.
6. When is a TN-C system used in actual practice?
Documentation
Textbooks, table manuals
Operating instructions
Data sheets
Internet
Equipment overview
Quantity Component
1 Mains supply
1 Service connection
1 Suitable measuring instrument (e.g. multimeter)
2 Laboratory safety cables
a) Complete the diagram so that a TN-C system is created.
Designate the individual conductors.
M3
Exercise 1 – Measurements at power supply systems
© Festo Didactic GmbH & Co. KG 567309 Name: __________________________________ Date: ____________ 7
b) Measuring circuit layout
GNDPE
L1
L1
L2
L2
L3
L3
N
PE/PEN
N
VCC
PE
L1
L2
L3
N
L1
L2
L3
N
PE/PEN
GND
Probe
GND
L1 L2 L3 N PE
L1 L2 L3 N PE
kWh
20m
1,5Ω 47Ω 470Ω 1kΩ 2,7kΩ
N
PE
L
PE
VCCVCC
4
5
mS
UL= 50
VACmAMΩ
N PE L
battery test
L-NL-PEN-PE
VDCVACkDΩHz
TEST
RCD
RLORE
ZLRISO ΔTIΔ
select
clear
recall
store
ZRZLZS
PSC
UN
IK
UF
REPEFC
IKRE
ZERO
Var
AUTOx1/2x1x5
mA300
180°
500
VOLTS2500
1000
1000
0~ S
memory recall +!
ZERO
MEMORY
TEST
F1
F2
F3
F4
V
1,5Ω
Performing the measurement – measuring voltage and frequency
1. Set the rotary switch to the V position.
2. Use the L (red) and PE (green) sockets for this test.
Use the laboratory safety cables.
• The main display (top) indicates alternating voltage.
• The secondary display (bottom) indicates line frequency.
• Press F1 in order to switch the displayed voltage to L-PE.
• Repatch the laboratory safety cables in order to perform the required measurements.
Exercise 1 – Measurements at power supply systems
8 Name: __________________________________ Date: ____________ © Festo Didactic GmbH & Co. KG 567309
c) Measure the voltages in the TN-C system
Attention
You will be working with line voltage while performing the measurements.
Do not switch on until the entire circuit has been completely wired!
Conductors Standard value Measured value
L1 – L2
L1 – L3
L2 – L3
L1 – PEN
L2 – PEN
L3 – PEN
Voltages in the TN-C system
d) Evaluate the measured values.
e) What needs to be observed in actual practice in the case of the TN-C system?
Exercise 1 – Measurements at power supply systems
© Festo Didactic GmbH & Co. KG 567309 Name: __________________________________ Date: ____________ 9
2. TN-C-S system
Project assignments
1. Set up a TN-C-S system at your mains connection board.
2. Complete the entries in the worksheet so that a TN-C-S system is created.
3. Measure all possible voltages in the TN-C-S system with a suitable measuring instrument.
4. Enter the measured values to the table furnished to this end.
5. Evaluate the measured values.
6. When is a TN-C-S system used in actual practice?
Documentation
Textbooks, table manuals
Operating instructions
Data sheets
Internet
Equipment overview
Quantity Component
1 Mains supply
1 Service connection
1 Suitable measuring instrument (e.g. multimeter)
2 Laboratory safety cables
Exercise 1 – Measurements at power supply systems
10 Name: __________________________________ Date: ____________ © Festo Didactic GmbH & Co. KG 567309
a) Complete the diagram so that a TN-C-S system is created.
Designate the individual conductors.
M3
b) Sketch the fault loop in the event of a fault to frame into the graphic below.
N
PEPEN
L3
L2
L1
RARB
Exercise 1 – Measurements at power supply systems
© Festo Didactic GmbH & Co. KG 567309 Name: __________________________________ Date: ____________ 11
c) Measuring circuit layout
GNDPE
L1
L1
L2
L2
L3
L3
N
PE/PEN
N
VCC
PE
L1
L2
L3
N
L1
L2
L3
N
PE/PEN
GND
Probe
GND
L1 L2 L3 N PE
L1 L2 L3 N PE
kWh
20m
1,5Ω 47Ω 470Ω 1kΩ 2,7kΩ
N
PE
L
PE
VCCVCC
4
5
UL= 50
V
N PE L
battery test
L-N
Hz
TEST
ZERO
MEMORY
TEST
F1
F2
F3
F4
V
1,5Ω
Performing the measurement – measuring voltage and frequency
1. Set the rotary switch to the V position.
2. Use all sockets for this test (red, blue and green).
Use the laboratory safety cables.
• The main display (top) indicates alternating voltage.
• The secondary display (bottom) indicates line frequency.
• Press F1 in order to switch displayed voltage back and forth amongst L-PE, L-N and N-PE.
• Repatch the laboratory safety cables in order to perform the required measurements.
Exercise 1 – Measurements at power supply systems
12 Name: __________________________________ Date: ____________ © Festo Didactic GmbH & Co. KG 567309
d) Measure the voltages in the TN-C-S system
Attention
You will be working with line voltage while performing the measurements.
Do not switch on until the entire circuit has been completely wired!
Conductors Standard value Measured value
L1 – L2
L2 – L3
L1 – N
L2 – N
L3 – N
L1 – PE
L2 – PE
L3 – PE
Voltages in the TN-C-S system
e) Evaluate the measured values.
Exercise 1 – Measurements at power supply systems
© Festo Didactic GmbH & Co. KG 567309 Name: __________________________________ Date: ____________ 13
f) What needs to be observed in actual practice in the case of the TN-C-S system?
Exercise 1 – Measurements at power supply systems
14 Name: __________________________________ Date: ____________ © Festo Didactic GmbH & Co. KG 567309
3. TT system
Project assignments
1. Set up a TT system at your mains connection board.
2. Complete the entries in the worksheet so that a TT system is created.
3. Measure all possible voltages in the TT system with a suitable measuring instrument.
4. Enter the measured values to the table furnished to this end.
5. Evaluate the measured values.
6. When is a TT system used in actual practice?
7. Why are residual current devices (RCDs) mandatorily stipulated in TT systems?
8. Examine the dependence of contact voltage on grounding resistance and fault current.
Documentation
Textbooks, table manuals
Operating instructions
Data sheets
Internet
Equipment overview
Quantity Component
1 Mains supply
1 Service connection
1 Suitable measuring instrument (e.g. multimeter)
2 Laboratory safety cables
Exercise 1 – Measurements at power supply systems
© Festo Didactic GmbH & Co. KG 567309 Name: __________________________________ Date: ____________ 15
Information
Residual current devices (RCDs) are mandatorily stipulated in TT systems!
N
N
PE
L3
L3
L2
L2
L1
L1
M
RCD RCDRCD
RARARB RA
Connection of consumers via RCDs in the TT system
Exercise 1 – Measurements at power supply systems
16 Name: __________________________________ Date: ____________ © Festo Didactic GmbH & Co. KG 567309
a) Complete the diagram so that a TT system is created.
Designate the individual conductors.
M3
b) Measuring circuit layout
GNDPE
L1
L1
L2
L2
L3
L3
N
PE/PEN
N
VCC
PE
L1
L2
L3
N
L1
L2
L3
N
PE/PEN
GND
Probe
GND
L1 L2 L3 N PE
L1 L2 L3 N PE
kWh
20m
1,5Ω 47Ω 470Ω 1kΩ 2,7kΩ
N
PE
L
PE
VCCVCC
4
5
mS
UL= 50
VACmAMΩ
N PE L
battery test
L-NL-PEN-PE
VDCVACkDΩHz
TEST
RCD
RLORE
ZLRISO ΔTIΔ
select
clear
recall
store
ZRZLZS
PSC
UN
IK
UF
REPEFC
IKRE
ZERO
Var
AUTOx1/2x1x5
mA300
180°
500
VOLTS2500
1000
1000
0~ S
memory recall +!
ZERO
MEMORY
TEST
F1
F2
F3
F4
V
1,5Ω
Exercise 1 – Measurements at power supply systems
© Festo Didactic GmbH & Co. KG 567309 Name: __________________________________ Date: ____________ 17
Performing the measurement – measuring voltage and frequency
1. Set the rotary switch to the V position.
2. Use the L (red) and N (blue) sockets for this test.
Use the laboratory safety cables.
• The main display (top) indicates alternating voltage.
• The secondary display (bottom) indicates line frequency.
• Press F1 in order to switch displayed voltage back and forth amongst L-PE, L-N and N-PE.
• Repatch the laboratory safety cables in order to perform the required measurements.
c) Measure the voltages in the TT system
Attention
You will be working with line voltage while performing the measurements.
Do not switch on until the entire circuit has been completely wired!
Conductors Standard value Measured value
L1 – L2
L2 – L3
L3 – L1
L1 – N
L2 – N
L3 – N
Voltages in the TT system
Exercise 1 – Measurements at power supply systems
18 Name: __________________________________ Date: ____________ © Festo Didactic GmbH & Co. KG 567309
d) Evaluate the measured values.
e) What needs to be observed in actual practice in the case of the TT system?
f) Why are residual current devices (RCDs) mandatorily stipulated in TT systems?
Exercise 1 – Measurements at power supply systems
© Festo Didactic GmbH & Co. KG 567309 Name: __________________________________ Date: ____________ 19
g) Fault current is shown in the following table as measured for various grounding resistance values.
Use these values to calculate the respective contact voltages.
Grounding resistance Fault current Contact voltage
1 k 0.21 A
400 0.48 A
200 0.82 A
100 1.42 A
40 2.15 A
20 2.5 A
h) Evaluate the individual values.
Exercise 1 – Measurements at power supply systems
20 Name: __________________________________ Date: ____________ © Festo Didactic GmbH & Co. KG 567309
4. IT system
Project assignments
1. Complete the entries in the worksheet so that an IT system is created.
2. Set up an IT system with the help of the mains connection board and the IT board.
3. Measure all possible voltages in the IT system with a multimeter, and enter the values to the table
provided for this purpose.
4. Evaluate the measured values.
5. The transformer in the IT board is designated Dyn5. Explain this designation.
6. Explain when and where the IT system is used in actual practice.
7. Why are insulation monitoring devices (IMDs) mandatorily stipulated in IT systems?
8. Describe the insulation monitoring function.
9. Start up the IT system. Set the IMD to a threshold value of approximately 60 k. Generate an earth fault
with the potentiometer (500 k) and select various resistance values at the ohmmeter
(500 k, 200 k, 100 k, 50 k). Describe the reaction of the IMD.
10. Two RCDs (30 mA and 300 mA) are used for shutting down the IT system.
Supplement the IT system with the two RCD boards. Simulate an earth fault from L to PE at the 300 mA
RCD via the potentiometer (500 k) (first fault). Reset the acoustic signal and simulate an earth fault
from L2 to PE downstream from the 30 mA RCD (second fault). Explain how the IT system reacts.
11. Which tasks have to be completed when testing the IT system in accordance with IEC?
Documentation
Textbooks, table manuals
Operating instructions
Data sheets
Internet
Equipment overview
Quantity Component
1 Mains supply
1 IT system
1 RCD board (300 mA, 30 mA)
1 Suitable measuring instrument (e.g. multimeter)
2 Laboratory safety cables
Exercise 1 – Measurements at power supply systems
© Festo Didactic GmbH & Co. KG 567309 Name: __________________________________ Date: ____________ 21
Attention
There is no connection between active conductors and grounded parts in the IT system.
The bodies included in the electrical system are grounded.
Insulation monitoring devices (IMDs) are mandatorily stipulated in IT systems.
a) Complete the entries in the worksheet so that an IT system is created. Designate the individual
conductors.
Z <
M3
Z: impedance
Exercise 1 – Measurements at power supply systems
22 Name: __________________________________ Date: ____________ © Festo Didactic GmbH & Co. KG 567309
b) Set up an IT system with the help of the mains connection board and the IT board.
GNDPE
L1
L1
L2
L2
L3
L3
N
PE/PEN
N
VCC
1,5Ω
PE
L1
L2
L3
N
L1
L2
L3
GNDGND
10k�
500k�
1,5�
1,5�
1,5�
1,5�
VCC VCC
L3L2L1N
5 4
+
ONTest
Reset
AL
RAL
mS
UL= 50
VACmAMΩ
N PE L
battery test
L-NL-PEN-PE
VDCVACkDΩHz
TEST
RCD
RLORE
ZLRISO ΔTIΔ
select
clear
recall
store
ZRZLZS
PSC
UN
IK
UF
REPEFC
IKRE
ZERO
Var
AUTOx1/2x1x5
mA300
180°
500
VOLTS2500
1000
1000
0~ S
memory recall +!
ZERO
MEMORY
TEST
F1
F2
F3
F4
V
Performing the measurement – measuring voltage and frequency
1. Set the rotary switch to the V position.
2. Use all sockets for this test (red, blue and green).
Use the laboratory safety cables.
• The main display (top) indicates alternating voltage.
• The secondary display (bottom) indicates line frequency.
• Press F1 in order to switch displayed voltage back and forth amongst L-PE, L-N and N-PE.
• Repatch the laboratory safety cables in order to perform the required measurements.
Exercise 1 – Measurements at power supply systems
© Festo Didactic GmbH & Co. KG 567309 Name: __________________________________ Date: ____________ 23
c) Measure all possible voltages in the IT system with a multimeter, and enter the values to the table
provided for this purpose.
Attention
You will be working with line voltage while performing the measurements.
Do not switch on until the entire circuit has been completely wired!
Conductors Standard value Measured value
L1 – L2
L2 – L3
L3 – L1
L1 – N
L2 – N
L3 – N
L1 – PE
L2 – PE
L3 – PE
Voltages in the IT system
Exercise 1 – Measurements at power supply systems
24 Name: __________________________________ Date: ____________ © Festo Didactic GmbH & Co. KG 567309
d) Evaluate the measured values.
e) The transformer in the IT board is designated Dyn5. Explain this designation.
f) Explain when and where the IT system is used in actual practice.
Exercise 1 – Measurements at power supply systems
© Festo Didactic GmbH & Co. KG 567309 Name: __________________________________ Date: ____________ 25
g) Why are insulation monitoring devices (IMDs) mandatorily stipulated in IT systems?
h) Describe the insulation monitoring function.
Insulation monitoring device (IMD)
Exercise 1 – Measurements at power supply systems
26 Name: __________________________________ Date: ____________ © Festo Didactic GmbH & Co. KG 567309
i) Reaction of the IMD
j) Reaction of the IT system to fault 1 and fault 2
Exercise 1 – Measurements at power supply systems
© Festo Didactic GmbH & Co. KG 567309 Name: __________________________________ Date: ____________ 27
k) Which tasks have to be completed for initial testing of the IT system in accordance with IEC?
Note
IEC regulations concerning insulation monitoring:
• IEC 60364-1: Protection against indirect contact with shut-down and indication
• IEC 60364-7-710: Electrical safety in medical locations
Exercise 1 – Measurements at power supply systems
28 Name: __________________________________ Date: ____________ © Festo Didactic GmbH & Co. KG 567309