Switchgears Command circuits and Devices

Switchgears Circuit Diagrams
Prepared By :
Bahman Farsadinejad
Rev.0
PreparedBy:BahmanFarsadinejad
1
Bahman
Farsadi
nejad
Digitally signed by
Bahman
Farsadinejad
DN: cn=Bahman
Farsadinejad,
email=farsadi@mec
oir.com, o=MECO
Date: 2018.03.06
13:46:05 +03'30'

Electrical circuit
•Power circuit
•Control
circuit
Electrical
circuit
2

Electrical circuit
 Power circuits are required for carrying power to or from heavy
electrical equipments like motors, alternators, or any electrical
installation.
3

Electrical circuit
A control circuit is for the automatic control of equipment, for
safety interlocking, and sequencing the operations of the plant
equipment and machines.
4

Electrical circuit
• Reading and understanding electrical drawings
• To read and understand electrical drawings, it is
necessary to know the following:
 Symbols used for representing electrical devices
 Their interconnections, legends, terminology, and abbreviations
 Sheet numbering and column format for each sheet
 Wire and terminal numbering (an important aspect in understanding
electrical drawings).
5

Electrical circuit
• Symbols used for representing electrical devices
6

Electrical circuit
• Symbols used for representing electrical devices
7

Electrical circuit
Things to look for in an electrical drawing
1. The symbols shown for a
device in a circuit represent its
de-energized state when no
power is applied.
8

Electrical circuit
2. An electrical drawing has a sheet number and each sheet is divided into
columns listed vertically as A, B, C, D and horizontally as 1, 2, 3, 4.
9

Electrical circuit
3. In order to identify different coils and their contacts a letter such as K1, K2
or C1, C2 is placed next to the circle of the coil.
10

Electrical circuit
4. Particular relay contacts may be used in different circuits at different
locations.
11

Electrical circuit
5. In general, a heavy line is used to show high current-carrying conductors
(mains supply lines, motor connection leads). In contrast, light-looking
lines are used to represent low current-carrying conductors (control circuit
lines).
12

Electrical circuit
6. Control circuit power lines are shown as L1 and L2
7. Conductors intersecting each other with no electrical junction in between
are represented with an intersection without any dot.
8. A broken line in an electrical circuit represents mechanical action.
13

Electrical circuit
9. Dotted lines are used to differentiate an enclosure from field devices.
10. A wiring diagram of electric equipment represents the physical location of the
various devices and their interconnections.
11. In an electrical drawing, conductors are marked with cross lines and
dimensions of conductors are given alongside. This is used to represent the
conductor size of a particular section in a drawing.
14

Circuit Diagram
Motor Starter
15

Typical circuits with DOL contactors
16

Typical circuits with DOL contactors
Method of operation: Actuation
of pushbutton I energizes the
coil of contactor Q11. The
contactor switches on the
motor and maintains itself after
the button is enabled via its
own auxiliary contact Q11/14-
13 and pushbutton 0 (three-
wirecontrolcontact).Contactor
Q11 is de-energized, in the
normal course of events, by
actuation of pushbutton 0. In
the event of an overload, it is
de-energized via the normally
closed contact 95-96 on the
overload relay F2. The coil
current is interrupted, and
contactor Q11 switches
the motor off.
17

Typical circuit with bridging of overload relay during
starting
18

Typical circuit with bridging of overload relay during
starting
• Function
Actuation of pushbutton I energizes
bridging contactor Q14 which then
maintains itself via Q14/13-14. At the same
time, voltage is applied to the timing relay
K1. The mains contactor Q11 is closed by
Q14/44-43 and maintains itself via
Q11/14-13. When the set time – which
corresponds to the start-up time of the
motor - has elapsed, the bridging contactor
Q14 is disconnected by K1/16-15. K1 is
likewise disconnected and, exactly as Q14,
can only be energized again after the motor
has been switched off by pressing
pushbutton 0. The N/C Q11/22-21 prevents
Q14 and K1 closing whilst the motor is
running. In the event of an overload,
normally closed contact 95-96 on the
overload relay F2 effects de-energization.
19

2 operating directions, reversing contactor
20

2 operating directions, reversing contactor
Changing direction of rotation after actuation
of the 0 pushbutton
Changing direction of rotation without
actuation of the 0 pushbutton
Q11: Mains contactor, clockwise
Q12: Mains contactor,
anticlockwise operation
21

Operating direction and two speeds (reversing contactor)
22

23

• Method of operation: Forward travel is initiated by pressing
pushbutton I or II according to the speed required. Pushbutton I
switches on the feed motion via Q17. Q17 maintains itself via its
N/O 13-14. If the feed movement is to occur at high-speed star
contactor Q23 is energized via pushbutton II which energizes the
high speed contactor Q21 via its N/O Q23/13-14. Both of the
contactors are maintained via Q21/13-14. A direct switch over from
feed to high-speed during the process is possible. High-speed
reverse is initiated by pushbutton III. Contactor relay K1 picks up
and energizes star contactor Q23 via K1/14-13. High-speed
contactor Q22 is energized via normally open contacts K1/43-44
and Q23/44-43, and is maintained via Q22/14-13. The reverse
motion can only be stopped via pushbutton 0. Direct
changeover/reversal is not possible.
24

Automatic star-delta switches
25

26

• Function
Pushbutton I energizes timing relay K1. The normally open contact K1/17-
18 (instantaneous contact) which applies voltage to star contactor Q13,
which closes and applies voltage to mains contactorQ11vianormally open
contact Q13/14-13. Q11 and Q13 maintain themselves via the N/O
Q11/14-13 and Q11/44-43. Q11 applies mains voltage to motor M1 in star
connection. When the set changeover time has elapsed, K1/17-18 opens
the circuit of Q13 and after 50 ms closes the circuit of Q15 via K1/17-28.
Star contactor Q13 drops out. Delta contactor Q15 closes and switches
motor M1 to full mains voltage. At the same time, normally closed contact
Q15/22-21 interrupts the circuit of Q13 thus interlocking against renewed
switching on while the motor is running. The motor cannot start up again
unless it has previously been disconnected by pushbutton 0, or in the
event of an overload by the normally closed contact 95-96 of overload
relay F2, or via normally open contact 13-14 of the motor-protective
circuit-breaker or standard circuit-breaker.
27

28

2 operating directions
29

Three-phase motor starter with mains
contactor and resistors,2-stage, 3-phase version
30

31

• Function
Pushbutton I energizes step contactor Q16 and timing relay K1. Q16/14-13
– self-maintaining through Q11, Q11/32-31 and pushbutton 0. The motor
is connected to the supply with upstream resistors R1 + R2. When the set
starting time has elapsed, normally open contact K1/15-18
energizes Q17. Step contactor Q17 bypasses the starting stage R1. At the
same time, normally open contact Q17/14-13 energizes K2. When the set
starting time has elapsed, K2/15-18 energizes mains contactor Q11. This
bypasses the second starting stage R2, and the motor runs at the rated
speed. Q11 maintains itself via Q11/14-13. Q16, Q17, K1 and K2 are de-
energized by normally closed contacts Q11/22-21 and Q11/32-31. The
motor is switched off with pushbutton 0. In the event of an overload,
normally closed contact 95-96 of the overload relay F2 or normally open
contact 13-14 of the motor-protective circuit-breaker switch off the motor.
Step contactor Q17, resistor R2 and timing relay K1 are omitted in single-
stage starting circuits. Timing relay K2 is connected directly to Q16/13 and
resistor R2 is connected by means of its terminals U1, V1 and W1 to
Q11/2, 4, 6.
32

Three-phase motor starter with mains contactor and
starting transformer, 1-stage, 3-phase
33

34

• Function
Pressing pushbutton I simultaneously energizes star contactor Q13,
timing relay K1 and, via normally open contact Q13/13-14, step
contactor Q16, and are maintained via K1/13-14. When K1 has
elapsed, normally closed contact K1/55-56 de-energizes star
contactor Q13, and Q16 –via normally open contact Q13/13-14: The
starting transformer is disconnected, and the motor runs at the
rated speed.
The motor cannot start up again unless previously switched off by
actuation of pushbutton 0, or in the event of an overload, by N/C
95-96 of the overload relay F2. With two-wire control, overload
relay F2 must always be set to reclosing lockout.If the motor has
been switched off by F2,the motor cannot start up again unless the
reclosing lockout is released.
35

Three-phase automatic rotor starters
3-stage, rotor 3-phase
36

37

38

• Function
Pushbutton I energizes mains contactor Q11: N/O Q11/14-13 transfers the voltage,
Q11/44-43 energizes timing relay K1. The motor is connected to the supply system
with rotor resistors R1 + R2 + R3 in series. When the set starting time has elapsed,
normally open contact K1/15-18 energizes Q14. Step contactor Q14 short-circuits
starting stage R1 and via Q14/14-13 energizes timing relay K2. When the set
starting time has elapsed, K2/15-18 energizes step contactor Q12, which
short-circuits starting stage R2 and via Q12/14-13 energizes timing relay K3. When
the set starting time has elapsed, K3/15-18 energizes final step contactor Q13,
which is maintained via Q13/14-13, Step contactors Q14 and Q12 as well as timing
relays K1, K2 and K3 are de-energized via Q13. Final step contactor Q13 short-
circuits the rotor slip rings: the motor operates with rated speed. The motor is
switched off either by pushbutton 0, or in the event of an overload, by N/C 95-96
of the overload relay F2 or N/O 13-14 of the motor-protective circuit-breaker or
circuit-breaker. Step contactors Q13 and/or Q12 with their resistors R3, R2 and
timing relays K3, K2 are omitted in single-stage or two-stage starting circuits. The
rotor is then connected to the resistance terminals U, V, W2 or U, V, W1. The
references for step contactors and timing relays in the wiring diagrams are then
changed from Q13, Q12 to Q12, Q11 or to Q13, Q11 as appropriate. When there
are more than three stages, the additional step contactors, timing relays and
resistors have appropriate increasing designations.
39

CONTROL VOLTAGE
TRANSFORMER SIZING
40

CONTROL VOLTAGE TRANSFORMER SIZING
The use of an industrial control transformer
is absolutely essential for the safe and
reliable operation of control devices.
Electromagnetic control components such
as solenoids, contactors and timers
place heavy demands on transformers
powering them. These increased demands
take place during start-up and the
energizing of control sequences
due to the inductive nature of most control
devices.
This results in very high inrush currents
flowing through the transformer during
start-up phases of control operation.
41

• STEP 1
Determine the total sealed (steady state) VA load
of the control circuit. Add the continuous VA
requirements of the maximum number of
components that will be energized at any given
time. Include both electromagnetic
(coils,solenoids, etc.) and non-electromagnetic
components (pilot lights, timers, etc.). Sealed VA
data is available from the component
manufacturers. If only current is known, simply
multiply current by voltage to get VA.
42

• STEP 2
Determine the total inrush VA load of the control
circuit. Add together the inrush VA ratings of the
electromagnetic components (coils, solenoids,
etc.) that will be energized simultaneously. Inrush
VA data is usually available from the component
manufacturers. Also, add the normal VA
requirements of non-electromagnetic
components (pilot lights,timers, etc.) that will be
energized at the same time.
43

• Method 1: The most accurate formula for determining
Selection Inrush VA is to calculate the total
inrush VA vectorially:
Selection inrush VA =
• Method 2: While usually resulting in a slightly
oversized transformer, a simpler method to determine
Selection Inrush VA is to calculate it arithmetically:
Selection inrush VA =
VA sealed + VA inrush
44

• STEP 3
Refer to the Regulation Data Chart. If the supply
circuit (primary) voltage is reasonably stable and
fluctuates no more than ±5%, refer to the 90%
Secondary Voltage column. If it fluctuates as
much as ±10%, refer to the 95% Secondary
Voltage column. NEMA standards require all
electromagnetic devices to operate successfully
at 85% of rated voltage. The 90% Secondary
Voltage column is most commonly used for
transformer selection.
45

• STEP 4
In the selected column of the Regulation Data Chart,
locate the inrush VA closest to,but not less than, the
inrush VA of the control circuit. Read to the far left side
of the chart to determine the continuous nominal VA
nameplate rating of the transformer needed. The
secondary voltage delivered under inrush conditions
will be a minimum of 85%, 90%, or 95% of rated
secondary voltage, depending on the column selected
from the Regulation Data Chart. The total sealed VA of
the control circuit must not exceed the nominal VA
rating of the transformer selected.
46

47

• STEP 5
Determine the proper transformer model
number from the catalog. Make sure your
selection meets the following conditions:
1. Has the proper primary and secondary
voltage
2. Exceeds the inrush VA demands
3. Has a nameplate VA that exceeds the
sealed VA requirements
48

49

50

51

Some of command Circuit
Devices
52

Earthfault Relay
• Damage to the insulation of motors is frequently caused by
high voltage spikes.
• The sources may be switching transients from the supply
network, capacitor discharging, power electronics devices
or lightning strikes.
• Other causes are ageing and continuous or cyclical overload
as well as mechanical vibrations and foreign particles.
• In most cases, insulation damage results in shorting against
the grounded parts of the machine.
• In grounded supply systems, the ground currents can
quickly reach very high values.
• The prompt detection and protective shutdown of a ground
fault limits the extent of the resulting damage and helps to
reduce outages and repair costs.
53

Earthfault Relay
• A relatively simple ground fault protection method measures the zero
sequence current component of the current transformer-secondary
currents (“Holmgreen”-circuit, Fig. below).Because of the tolerances of
current transformers and of the influence the 3rd harmonic a sensitivity of
10 % can be achieved at best, typically around 30 %. This method is thus
also limited to application in solid grounded networks.
54

Siemens Residual current monitoring
The 3UG46 24 residual current monitoring
relay is used together with the 3UL22
summation current transformer for plant
monitoring.
The 3UL22 summation current transformers
detect fault currents in machines and plants.
Together with the 3UG46 24 residual
current monitoring relay or the SIMOCODE 3UF
motor management and control device they
enable residual-current and ground-fault
monitoring.
55

Siemens Residual current monitoring
56

Under/Over Voltage Relay
57

58

3UG4513
Monitoring Relays
for Phase-Sequence
and Undervoltage Monitoring
59

Suppressor circuit
60

Suppressor circuit
• When switching magnetic loads with high inductance such as for
example contactor coils, in spite of the above considerations,
switching transients with magnitudes of several kV and with rise-
times in the range of μs to ns can occur that may interfere with the
proper functioning of other devices.
• During the opening of the controlling contacts, there occur
repeated restrikes (shower discharges), as the inductance of the coil
maintains the current flow and the opening contact does not
instantaneously attain its full withstand voltage . These shower
discharges also increase wear on the switching control contact.
With respect to the interference effect, it is not only the size of the
overvoltage that is generated that is critical but also, in view of the
extremely short reaction times of electronic circuits, its rise and fall
time. Rapid signals couple via stray capacitances with other signal
circuits.
61

Suppressor circuit
Oscillogram of the voltage characteristic during circuit
breaking of a 24 V coil without protection circuit
62

Suppressor circuit
• The best countermeasure is to deal with the interference at the source. To this end
suppressor modules are offered for interference-producing coils, designed as plug-
on or wired add-ons or integrated in the contactor. Below Table provides a
summary of the alternatives and their most important features. Measures that
only limit the amplitude of the overvoltage are also effective with respect to
dynamic interference (to a limited extent) as they reduce the duration of the
shower discharges and limit their amplitude.
63

Suppressor circuit
Oscillogram of the voltage characteristic during circuit
breaking of a 24 V coil with protection circuits
64

Current Transformer
• Window – Type
Up to 4000 Amp
Round conductors up to 23 ∅
65

Current Transformer
• Bar type
Current Transformer
66

Current Transformer
• Ring Type Current
Transformers
(Toroidal)
The following information is required when
ordering ring type measuring and protection
current transformers according to IEC60044-1:
a- Transformer ratio
b- The VA burden
c- Class(measuring), class of accuracy and
accuracy limit factor(ALF)
d- Minimum inner diameter
Up to 6000 Amp
67

Fast-acting lockout relay
Due to their quality, reliability and
design, these relays are optimal
for applications requiring high
reliability and availability
such as power stations,
substations, railway
and industrial plants. Typical
examples include petrochemical
industry, chemical industry,
cement industry, rolling mills etc.
7PA22
68

Fast-acting lockout relay
7PA22
Fast-acting lockout relay Description
The bistable 7PA22 is a fast-acting lockout
relay with eight changeover contacts and is
plugged into a mounting frame equipped
with a plug-in socket (type 7XP9010) with
screw-type terminals at the rear
69

Trip circuit supervision
The 7PA30 relay is equipped with
green LED and two changeover
contacts. It is applied for trip
circuit supervision in the open
and close position of the circuit-
breaker. It monitors the trip circuit,
the trip coil and the proper state
of the fuses and mini circuit-
breakers of the circuit.
7PA30
70

Trip circuit supervision
The 7PA30 indicates a trip circuit
failure with a time delay of 150
ms. The relay is always in an
energized condition, regardless of
the position of the circuit-breaker
(open/close).
In the event of actuation of the
relay, its unassigned contacts can
be used for:
– Blocking the circuit-breaker
connection
– Issuing the trip command to
another c.-b. upstream or to a
second trip coil of the same c.-b.
– Local or remote signaling
71

Incoming/Bus-tie Circuit
Diagrams
72

Schematic Diagram
• Legend And Abbreviations
• Heater & Lighting
• Auxiliary Voltage Distribution
• Power Circuit
• Measuring & sensor devices
• Closing and Opening Circuits
• Protection Relays
• Control Circuits
• Signaling Circuits
• Terminal Diagram
73

Schematic Diagram
74

Schematic Diagram
75

Schematic Diagram
• Heater & Lighting
76

Schematic Diagram
• Auxiliary Voltage Distribution
77

Schematic Diagram
• Power Circuit
78

Schematic Diagram
• Measuring & sensor devices
79

Schematic Diagram
• Closing and
Opening Circuits
80

Schematic Diagram
• Protection Relays
81

Schematic Diagram
• Control Circuits
82

Schematic Diagram
• Signaling Circuits
83

Schematic Diagram
• Terminal Diagram
84

Switchgears Command circuits and Devices

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