circuit breaker application & distribution systems - 2014
Post on 02-Oct-2015
31 Views
Preview:
DESCRIPTION
TRANSCRIPT
-
ABB Group March 12, 2014 | Slide 1
Lionel Ng, LPBS - Low Voltage Products
Welcome Technical Sharing Session
-
ABB Group March 12, 2014 | Slide 2
Lionel Ng, LPBS - Low Voltage Products, 2014
Electrical Installation Circuit Breaker Selection
-
As to be able to protect LV/MV transformers LV side, we must mainly
take into account:
Rated current of the protected transformer, LV side, from which
the rated current of the circuit breaker and the setting depend on
(In);
The maximum estimated short circuit current in the installation
point which defines the minimal breaking power of the protection
circuit breaker (Isc).
Protection of Transformers
-
Sn
In
Isc
U20
Protection of Transformers Switchboards with one transformer
The rated current of the transformers LV side is defined by the
following expression
where
Sn = rated power of the transformer [kVA]
U20 = rated secondary voltage (no load) of the transformer [V]
ln = rated current of the transformer, LV side [A]
In = Sn x 103
3 x U20
-
The full voltage three-phase short circuit current immediately after the LV
side of the transformer can be expressed by the following relation once we
suppose infinite power at the primary:
where
Ucc % = short circuit voltage of the transformer [%]
ln = rated current, LV side, [A]
lsc = three-phase rated short circuit current, LV side, [A]
Isc = In x 100
Ucc %
Protection of Transformers
The short circuit current is normally lesser than the deduced value if
the circuit breaker is installed at a certain distance by means of a cable
or bar connection, according to the connection impedance.
-
Circ
uit b
reaker B
I1 I2 I3
1 2 3
Isc2 + Isc3
Isc1 + Isc2 + Isc3
I4 I5
Circ
uit b
reaker A
Isc1
Protection of Transformers Switchboards with more than 1 transformer in Parallel
-
As far as the calculation of the rated current of the transformer is
concerned, the rules beforehand indicated are completely valid.
The minimum breaking capacity of each circuit breaker LV side must be
greater than the highest of the following values: (the example refers to
machine 1 of the figure and it is valid for the three machines in parallel):
lsc 1 (short circuit current of transformer 1) in case of fault
immediately downstream circuit breaker 1;
lsc2 + lsc3 (short circuit currents of transformer 2 and 3) in case of
fault immediately upstream circuit breaker 1;
Protection of Transformers
Circuit breakers l4 and l5 on the load side must have a short circuit
capacity greater than lsc1 + lsc2 + lsc3; naturally every transformer
contribution in the short circuit current calculation is to be lessened by the
connection line transformer - circuit breaker (to be defined case by case).
-
The choice of the circuit breakers for switching and protection of cables
means the perfect knowledge of:
rated operating line current lB
max admissable cable current lZ
presumed short circuit current in the point of installation of the circuit
breaker Icc
Protection of Cables
-
The correct circuit breaker must be selected to satisfy the following
conditions:
It must have a short circuit breaking capacity (lcu or eventually lcs) greater
or equal to the short circuit current lcc
It must use a protection release so that its overload setting current ln (l1)
satisfies the relation lB < ln < lZ (Oveload protection)
The let through energy (l2t) that flows through the circuit breaker must be
lesser or equal to the maximal one allowed by the cable (KS) (Short-
circuit protection)
Protection of Cables
-
It
Icc
Cable KS
Circuit breaker It
Icc max
Protection of Cables
-
As far as the verification required by IEC 60364, according to which
the overload protection must have an intervention current (lf) that
assures the operation for a value lesser than 1.45 lz (lf < 1.45 lz), we
must state that it is always verified for ABB Circuit breakers, since
according to IEC 60947-2 the required value is less than 1.3 ln.
Protection of Cables
-
LV protection devices
L function protection against
overload
Circuit Breaker Curves
-
S function protection against
delayed short-circuit
LV protection devices
Circuit Breaker Curves
-
LV protection devices
Circuit Breaker Curves
I function protection
against instantaneous
short-circuit
-
LV protection devices
Circuit Breaker Curves
G function protection
against earth-fault
-
A
B
C
Protection of Primary & Secondary Distribution
Selective Protection
The example emphasizes the need for co-
ordination between circuit breakers A and
B, such that in case of fault in C, only circuit
breaker B trips, thus leaving complete
continuity to the rest of the plant supplied
by the circuit breaker A.
Selectivity might be Total or Partial:
Total selectivity: only the circuit breaker B
trips for every current value lesser or equal to
the max short circuit current foreseen in C;
Partial selectivity: the circuit breaker B opens
only according to fault current lower than a
certain value; values that are equal or greater
than this will give the intervention of both
circuit breakers A and B.
-
Amperometric (Current) selectivity is obtained
by setting on different values the
instantaneous tripping currents of the circuit
breakers chain (greater values for upstream
circuit breakers)
Protection of Primary & Secondary Distribution
Selective Protection
A B
ImB ImA
ImA is the selectivity limit
-
Chronometric (Time) selectivity is obtained by
introducing intentionally always greater delays in
the intervention tripping timings of the upstream
circuit breakers in the chain.
Protection of Primary & Secondary Distribution
Selective Protection
Total selectivity
B A
t
-
Switchboard A
Switchboard B
400V
400V
2500 kVA
(fault current 57,5 kA)
E2N20 MS (disconnector)
E4S40
with PR121
E2N20
with PR121
T5H 630
with PR222
Protection of Primary & Secondary Distribution
-
Protection of Primary & Secondary Distribution
-
Protection of Primary & Secondary Distribution
-
A
B
C
Protection of Primary & Secondary Distribution
Back-up Protection
In the figure, the circuit breaker B, downstream in respect
with A, might have a short circuit breaking capacity lesser
than the presumed short circuit current in case of fault in
C if the circuit breaker A satisfies at all the two following
conditions:
It has a short circuit rating greater or equal to the
presumed short circuit current in its installation point and
obviously greater than the short circuit current in C
In case of fault in C with short circuit values greater
than the short circuit breaking capacity of circuit breaker
B, the circuit breaker A must limit the let through energy
by limiting it to a correct value than can be stood by
circuit breaker B and by the protected lines
-
The back-up protection is used in electric plants where operation continuity
is not a main need. This means that the up stream breaker will always trip
with or without the help from the down stream protection device. This
means the whole system including the sound parts of the installation will
be without power.
This co-ordination solution is used by those who need to contain the plant
costs by reducing the general performance in case of a fault.
Protection of Primary & Secondary Distribution
Back-up Protection
-
U Load
B
A
Ib = 1300 A
Icc = 65 kA
Icc 30 kA
Ib = 300 A
Protection of Primary & Secondary Distribution
Back-up Protection
Electrical characteristics of the employed circuit breakers
Reference Rated Type Rated Breaking Selectivity Back-up
current uninterrupted capacity limit limit
current
[A] Iu [A] Icu [kA] [kA] [kA]
A 1300 SACE Emax E2L16 1600 130
B 300 SACE Tmax T4N 320 320 36
36 (T) 65
-
50 kA !!!
T4S 250
T1N 160 * T1N 160 is 36 kA only mccb
Protection of Primary & Secondary Distribution
Back-up Protection
-
T6H 800 (70kA)
70 kA
T4H 250 (70kA)
Protection of Primary & Secondary Distribution
Selectivity
-
Rated operational voltage Ue: the value of voltage which
determines the application and to which all the other
parameters are referred to.
Rated uninterrupted current Iu: the value of current which the
device is able to carry for an indefinite time. It defines the size
of the CB
Rated current In: the value of current which characterizes the
protection release installed. Is often related to the rated
current of the load protected
T5N400 PR221DS-LS/I In 320
Iu In
Selection of Protective Devices Main electrical parameters
-
Rated ultimate short-circuit breaking capacity Icu: it is the
r.m.s. value of the symmetrical component of the short-circuit
current which the circuit-breaker is able to break (test cycle O-
t-CO)
Rated service short-circuit breaking capacity Ics: it is the r.m.s.
value of the symmetrical component of the shortcircuit current
which the circuit-breaker is able to break (O-t-CO-t-CO)
T5N400 PR221DS-LS/I In 320
Icu
Selection of Protective Devices Main electrical parameters
-
Rated short-circuit making capacity Icm: it is the maximum
prospective peak current which the circuit-breaker must be
able to make Icm=n x Icu
T5N400 PR221DS-LS/I In 320
Icu 36kA Icm 75.6 kA @415V
Selection of Protective Devices Main electrical parameters
-
Rated short-time withstand current Icw: it is the r.m.s. value of
the alternate current component which the circuit-breaker is
able to withstand without damages for a determined time,
preferred values being 1s and 3 s
Defined for category B only
Selection of Protective Devices Main electrical parameters
-
Selection of Protective Devices Main electrical parameters
-
Generalities about the main electrical parameters Dont forget
Ue Un Icu or Ics Ik Icm Ip
Ue, Icu, Ics, Icm?
Selection of Protective Devices Main electrical parameters
-
ABB Group March 12, 2014 | Slide 34
Lionel Ng, Low Voltage Products, 2014
Distribution systems Protection against indirect contact and earth fault
-
Agenda
Main definitions
Distribution systems and protection
against indirect contact and earth fault
ABB solutions for protection
against earth fault
Discrimination of the protections
against earth fault
-
Definitions
Indirect contact
Electric contact of persons with exposed-conductive-parts which have become live under fault condiction (deterioration)
Direct contact
Electric contact of persons with live parts
-
Definitions
Earth fault
The loss of insulation between normally live conductors and exposed-conductive-parts may generate a earth fault
Main causes of the loss of insulation:
time decay of dieletric properties
mechanical breaking
particularly aggressive environments
rodent action
overvoltages of atmospheric origin or due to switching
-
Definitions
Main effects of the earth fault current
energizing of exposed-conductive-
parts
localized electric arcs and consequent
overheatings
disturbances to telecommunication systems
erosion phenomena of earth electrodes
-
Definitions
Time-current zones of the effects of alternating current on the human body
A contact with a live part causes the flowing of current through
the human body, the danger of this current depends on its :
duration
size
Reversible pathological effects
No reaction
No physiological effect
Fibrillation risk greater than
50%
1
2
3
4
-
Definitions
Live part
Conductor or conductive part intended to be enegized in normal operation
Including a neutral conductor
By convetion not a PEN.
Exposed-conductive-part
Conductive part
Can be touched
Is not normally live
Can become live when basic insulation fails
-
Definitions
Basic insulation
Isolation of live part
Base protection against direct and indirect contact
Supplementary isolation
independent insulation applied in addition to basic insulation
Insures the protection when the basic insulation fails
Double isolation
comprises both basic insulation and supplementary insulation
Reinforced insulation
provides a degree of protection against electric shock equivalent to double insulation (unique insulation)
Fault current current which flows across a given point of fault resulting from an insulation
fault
-
Definitions
Live part
functional isolation: in an electrical device it insulates the parts at different potentials thus enabling operations
basic insulation is the insulation of the normally live parts
supplementary insulation is applied in addition to basic insulation in case of a failure of the last
reinforced insulation, a unique insulation which can guarantee the equivalent protection degree which can be provided by basic insulation plus supplementary insulation
Double insulation: comprises both basic insulation and supplementary insulation
+
-
Definitions
Reference earth
part of the Earth considered as conductive, the electric potential of which is conventionally taken as zero
Earth electrode
conductive part, which may be embedded in a specific conductive medium, e.g. concrete or coke, in electric contact with the Earth
Earthing resistance
resistance between the main earth collector (or node) and the Earth
-
Definitions
L1
L2
L3
N PE
Protective conductor PE
conductor provided for purposes of safety (protection against electric shock)
it connects:
exposed-conductive-parts
main earth collector (or node)
earth electrode
earthed point of the source or artificial neutral
PEN conductor
combines the functions of both a PE conductor and a neutral conductors
Residual current:
vectorial sum of the values of the electric currents in all live conductors
Id = IL1+ IL2+ IL3+ IN
-
Classification of electrical distribution systems
Protection against indirect contact
Protection throught automatic disconnection :
CBs with thermomagnetic or electronic releases;
CBs with electronic releases with G function against earth fault
CBs with residual current devices integrated
Residual current circuit breaker
Residual current releases
protection without automatic disconnection:
Protection by double or reinforced insulation;
Protection by earth-free local equipotential bonding;
Protection by electrical separation for the supply of only one item of current-using equipment
Protection by electrical separation for the supply of more than one item of current-using equipment
-
Classification of electrical distribution systems
The IEC 60364-3 classifies the electrical systems with the combination of two letters
The first letter indicates the relationship of the power system to earth
T direct connection to earth of one point
I all live parts isolated from earth or one point connected to earth through an impedance
The second letter indicates the relationship of the exposed-conductive- parts of the installation to earth
T direct connection to earth
N direct electrical connection of the exposed-conductive-parts to the earthed point of the power system
-
Classification of electrical distribution systems
Subsequent letters, if any, indicates the arrangement of neutral and protective
conductors
S neutral and protective functions provided by separate conductors
C neutral and protective functions combined in a single conductor (PEN
conductor)
PE N
PEN
-
Classification of electrical distribution systems
TT system
the neutral and the exposed-conductive-parts are connected to
earth electrodes electrically independent
-
Classification of electrical distribution systems
TT system
The earth fault current returns to the power supply node through the soil
-
Classification of electrical distribution systems
TT system
The exposed-conductive-part assumes the potential UT = Ik RA
The person touching the exposed-conductive-part is subjected to the voltage UT
Ik
-
Classification of electrical distribution systems
Condition to be fulfilled :
Ra is the total resistance of the earth electrode and of the protective conductor of the exposed-conductive-parts
IDn is the rated residual operating current of the residual current circuit- breaker
the time defined in the following table for the terminal circuits with a rated current In32A
0UIR na D
-
Classification of electrical distribution systems
Thanks to a more sensitive residual current device, from a pratical point of view it will be easier to realize an earthing system coordinated with the characteristics of the device itself. This table shows the maximum values of earth resistance which can be obtained with residual current devices and making reference to a common environment (50V)
-
toroid
trip coil
test button
main contact
resistance
electronic circuit (if any)
How an RCD works
-
How an RCD works
-
How the RCD works
TEST
-
Classification of electrical distribution systems
Condition to be fulfilled :
Zs is the total impedance of the loop;
Ia is the disconnection current in these time:
the time defined in the following table for the terminal circuits with a rated current In32A
0UIZ as
-
Conclusion about TT system
Domestic installations and similar, small industries with LV power supply
Typical value of earth fault currents 10 ~ 100A
The standards allow the use of:
CBs with inverse time tripping characteristics
CBs with instantaneus tripping characteristics
Residual current devices
If automatic disconnection cannot be obtained in compliance with the disconnection times of the table or within the conventional time, it shall be necessary to provide supplementary equipotential bonding connnected to earth, however the use of supplementary protective bonding does not exclude the need to disconnect the supply for other reasons, for example protection against fire, thermal stresses in equipment
Classification of electrical distribution systems
-
Classification of electrical distribution systems
TN-S system
the neutral and the exposed-conductive-parts are connected to the same earthing arrangement
the exposed-conductive-parts are connected to the earth electrode by means of the PE
N
PE
-
Classification of electrical distribution systems
TN-C system
the neutral and the exposed-conductive-parts are connected to the same
earthing arrangement
the exposed-conductive-parts are connected to the earth electrode by
means of the PEN
PEN
-
Classification of electrical distribution systems
TN system
the earth fault current returns to the power supply node without practically
affecting the earth electrode
the current is limited by the impedance of the fault loop
-
Classification of electrical distribution systems
TN system
It is necessary to interrupt the fault because person touching the exposed-conductive-part is subjected to the voltage UT
-
Classification of electrical distribution systems
Condition to be fulfilled :
Zs is the impedance of the fault loop
U0 is the nominal voltage to earth
Ia is the diconnection time in ampere of the protective devices within:
the time defined in the following table for the terminal circuits with a rated current In32A
0aS UIZ
-
Classification of electrical distribution systems
TN system: example
Un = 400 V (U0=230V)
This system supplies a terminal circuit with In>32A
Earth fault = 3 kA
-
Classification of electrical distribution systems
Conclusion about TN system:
Industries and big installations with MV power supply
Fault current values similar to those of the single-phase fault
The standard allow the use of:
Automaic devices against overcurrents
RCD or CBs with G function
In the TN-C systems disconnection of the neutral and use of the residual current devices or devices with similar operating principle (function G against earth fault) is not possible
if automatic disconnection cannot be obtained in compliance with the disconnection times of the table or within the conventional time, it shall be necessary to provide supplementary equipotential bonding connected to earth, however the use of supplementary protective bonding do not exclude the need to disconnect the supply for other reasons, for the example protection against fire, thermal stresses in equipment
-
Classification of electrical distribution systems
Why in TN-C system it is not possible to use RCD or
function G against earth fault?
TN-S
TN-C
-
Classification of electrical distribution systems
IT system
has no active parts directly earthed
may have live parts connected to earth through high value impedance
the exposed-conductive-parts are connected to an independent earth electrode
-
Classification of electrical distribution systems
Dieletric insulator+air
Electric field
Plate
Plate area
IT system
The earth fault current returns to the power supply through the earthing arrangement of the exposed-conductive-parts and the capacities to earth of the line conductors
the fault current value depends on the size of the installation
-
capacities to earth of the line conductors
capacitor
cable
plate area
dielectric insulator+air
plate area
electric field
electric field
plate area
plate area
dielectric
Classification of electrical distribution systems
-
Classification of electrical distribution systems
IT system
the automatic disconnection of the circuit is not necessary
condition to be fulfilled:
RE is the sum of the resistance, in ohms, of the earth electrode and protective conductor for exposed-conductive-parts;
Id is the fault current, in amperes, of the first fault of negligible impedance between a line conductor and an exposed-conductive-part; such value takes account of the leakage currents and of the total earthing impedance of the electrical installation
an insulation monitoring device shall be provided to indicate the presence of
fault.
VIR dE 50
-
Classification of electrical distribution systems
IT system
the occurrence of a first earth fault modifies the distribution system
two situations may occur in the event of a fault to earth
-
Classification of electrical distribution systems
IT system
the occurrence of a first earth fault modifies the distribution system
two situations may occur in the event of a fault to earth
-
Classification of electrical distribution systems
according to TT system
IT system
in the event of a second fault, the supply shall be disconnected
-
Classification of electrical distribution systems
according to TN system
IT system
in the event of a second fault, the supply shall be disconnected
-
Neutral distribuited:
Classification of electrical distribution systems
a
sI
UZ
2a
sI
UZ
2
0'
Neutral not distribuited:
U0= is the nominal voltage between line conductor and neutral conductor
U = is the nominal voltage between line conductor
Zs = is the impedance of the fault loop comprising the line conductor and the protective conductor of the circuit
Zs= is the impedance of the fault loop comprising the neutral conductor and the protective conductor of the circuit
Ia = is the current causing the operation of protective device within the time required for TN system
-
Classification of electrical distribution systems
Conclusion about IT system:
chemical and petrochemical industries, i.e. plants for
which service continuity is fundamental
fault currents A ~ 2A dependent on the size of the
installation
system suitable for the cases in which service continuity
must be assured
The presence of a first fault does not cause high current and/or currents dangerous for the people
-
A reliable and safe protection is realized by combining:
The protection functions against overcurrent with those against earth faults
An effective earthing arrangement
This choice allows to obtain:
Protection against indrect contact
A timely protection against earth falts of small value where prevention from fire risks is absolutely necessary
Protection Solution
-
Protection Solution
For an adequate protection against earth faults ABB has designed the following product categories:
Miniature circuit breaker
Residual current operated circuit-breakers with integral overcurrent protection DS201 & DS202;
Residual current operated circuit-breakers with integral
overcurrent protection DS200;
Residual current operated circuit-breakers with integral
overcurrent protection DS800
Residual current blocks DDA200
Residual current blocks DDA 60, DDA 70, DDA 90 (S290)
Residual current blocks DDA 800
Residual current circuit breaker F200
-
Protection Solution
Miniature circuit-breaker
Residual current operated circuit-breakers with integral
overcurrent protection DS201
-
Protection Solution
Miniature circuit-breaker
Residual current operated circuit-breakers with integral
overcurrent protection DS202
-
Protection Solution
Miniature circuit-breaker
Residual current operated circuit-breakers with
integral overcurrent protection DS200
-
Protection Solution
Miniature circuit-breaker
Residual block DDA200
-
Protection Solution
Miniature circuit breaker
Residual block DDA 60, DDA 70, DDA 90
-
Protection Solution
Miniature circuit breaker
Residual block DDA 800
-
Protection Solution
Miniature circuit breaker
Residual current circuit breaker F200
-
Protection Solution
For an adequate protection against earth faults
ABB SACE has designed the following product
categories:
Moulded case circuit breaker
RC221 residual current devices
RC222 residual caurrent devices
RC223 residual current devices
Electronic release LSIG: PR222, PR223
Electronic release LSIG: PR331, PR332
Electronic release LSIRc: PR332
Description
-
Moulded case circuit breaker
Residual current devices RC221, RC222, RC223
Protection Solution
-
Protection Solution
Moulded case circuit breaker
Electronic releases LSIG:
PR222: T2, T4, T5, T6
PR223: T4, T5, T6
PR331, PR332: T7
G function setting
I4= 0.2..1 x In
t4= 0.1.0.8 x In con I2t=k o t=k
(depending by the type of
release)
-
Protection Solution
G function:
currently used in MV/LV transformer substations to protect both transformers as well as distribution lines
guarantees selectivity with regard to the residual current releases located on the load side
can be used for protection against indirect contact, when allowed by the installation conditions
improve protection against earth faults with regard to the normal phase protections
-
Protection Solution
Moulded case circuit breaker
Electronic release PR332 LSIRc for T7
-
Protection Solution
Moulded case circuit breaker
Summary table
-
Protection Solution
For an adequate protection against earth faults
ABB has designed the following product
categories:
Air circuit breakers
Electronic releases LSIG: PR331, PR332, PR333
Electronic release LSIG: PR121, PR122, PR123
Electronic release LSIRc: PR332
Electronic release LSIRc: PR122
Description
-
Protection Solution
G function setting
I4= 0.2..1 x In
t4= 0.1.0.8 x In con I2t=k o t=k
(depending by the releases)
For an adequate protection against earth faults
ABB has designed the following product
categories:
Air circuit breakers
Electronic releases LSIG: PR331, PR332, PR333
Electronic releases LSIG: PR121, PR122, PR123
-
Protection Solution
For an adequate protection against earth faults
ABB has designed the following product
categories:
Air circuit breaker
Electronic releases LSIRc: PR332
Electronic releases LSIRc: PR122
-
Protection Solution
For an adequate protection against earth faults
ABB has designed the following product
categories
Residual current relay with external trasformer
SACE RCQ switchboard electronic residual current relay
Residual current relay for DIN rail: RD2 & RD3
-
Protection Solution
For an adequate protection against earth faults
ABB has designed the following product
categories
Residual current relay with external trasformer
SACE RCQ switchboard electronic residual current relay
-
Protection Solution
For an adequate protection against earth faults
ABB has designed the following product
categories
Residual current relay for DIN rail: RD2
-
Protection Solution
For an adequate protection against earth faults
ABB has designed the following product
categories
Residual current relay for DIN rail: RD3
-
Protection Solution
For an adequate protection against earth faults
ABB has designed the following product
categories
Front panel residual current relay: ELR
-
Two types of residual current discrimination
horizontal residual current discrimination
vertical residual current discrimination
Discrimination of the protections against earth fault
-
To ensure discrimination
for residual current CBs type S located on the supply side (in compliance with Standards IEC 61008-1 and IEC 61009)
downstream non-selective residual current CBs having In three times lower
for residual current electronic releases (RC 221/222/223, RCQ and RD2)
tripping times and currents of the device on the supply side are immediately higher than those of the device on the load side
Discrimination of the protections against earth fault
-
Example
E1N 1250 PR121/P-LSIG In=1250A 4p
T5N 400 PR222DS/P-LSI In =400A con RC222
T1B 160 TMD In=160A con RC221
Discrimination of the protections against earth fault
-
Example
Discrimination of the protections against earth fault
-
Domestic Installation (TT)
Application of RCD
IdRCCB
MCB Load
MCB Load
-
Industrial installation (TN-S)
long cables
CB+RC Id
Application of RCD
-
Protection function G or residual current protection?
the choice can be done taking in consideration:
the distribution system
the value of the fault current
RCD:
particularly suitable for protection of people
absolutely necessary
in TT systems (small fault current to earth)
earthing of the exposed-conductive-parts is deficient
normal protections are not sufficient to provide protection that falls within the limits set by the Standards
dangerous environmental conditions (e.g. excessive humidity)
Application of RCD
-
G function:
currently used in MV/LV transformer substations to protect both transformers as well as distribution lines
guarantees selectivity with regard to the residual current releases located on the load side
can be used for protection against indirect contact, when allowed by the installation conditions
improve protection against earth faults with regard to the normal phase protections
Application of RCD
-
Typical application:
all types of construction sites (building, naval, etc.)
mobile equipment or plants
hospital environments and operating rooms
excavations and mines
campground electric installations
pools, saunas, canteens and, generally, environments with high humidity levels
aquarium and fountain lighting
agricultural premises
school laboratories
Application of RCD
top related