Specifications are subject to change without notice (27.10.99)
1
Current and Voltage Controls
Product Description
1-phase AC plug-in power
metering relay. Measures
power and direction of the
mains from power plant or
generator. Connected to
Ordering Key
Housing
Type
Output
Power supply
1-phase AC power metering and
direction relay
Measures up to 132 kW
Knob-adjustable power level
Built-in adjustable timer function
Output: 10 A SPDT relay
Plug-in type module
S-housing
LED-indication for power supply and output ON
AC power supply
other Carlo Gavazzi modu-
les, this relay can act as an
element to avoid wrong
transmission of power.
Type Selection
Input Specifications
Input
Pins 5 & 7
0.4-4 V
p
max. 20 V from current trans-
former types MI 100 or MI 500
Measuring ranges
Type
Voltage range
Trans-
Current Power
(VAC)
former
range(A) range(kW)
S 1821 156 230
195 - 265
MI 100
10-100
2.7 - 26.5
MI 500
50-500
13.2 -132
S 1821 156 115
95 - 135
MI 100
10-100
1.35 -13.5
MI 500
50-500
6.8 - 67.5
S 1821 156 024
20 - 28
MI 100
10-100
0.3 - 2.8
MI 500
50-500
1.4 - 14
Output Specifications (cont.)
Mechanical life
30 x 10
6
operations
Electrical life
AC 1
2.5 x 10
5
operations
(at max. load)
Operating frequency
7200 operations/h
Dielectric strength
Dielectric voltage
2 kVAC (rms) (cont./elect.)
Rated impulse withstand volt.
4 kV (1.2/50 s) (cont./elect.)
(IEC 60664)
Voltage output
Pins 6 & 7
0.4 - 4 VDC, pin 6 pos.
(= 10-100% of average
power, provided correct
power direction) for e.g.
SM 125, S 178
Instrument output
Pins 7 & 11 pin 11 pos.
Impedance
3.9 k
Moving-coil instrument
Connection with 1 mA full
scale deflection
Internal resistance
110
, 100% average
power causes full scale
deflection
Output
SPDT relay
Rated insulation voltage
250 VAC (rms)
(cont./elect.)
Contact ratings (AgCdO)
(micro gap)
Resistive loads
AC 1
10 A/250 VAC (2500 VA)
DC 1
1 A/250 VDC (250 W)
or
10 A/25 VDC (250 W)
Small inductive loads AC 15
2.5 A/230 VAC
DC 13
5 A/24 VDC
1-Phase Power Control
Type S 1821
Plug
Output
Supply: 24 VAC
Supply: 115 VAC
Supply: 230 VAC
Circular
SPDT
S 1821 156 024
S 1821 156 115
S 1821 156 230
Output Specifications
S 1821 156 024
2
Specifications are subject to change without notice (27.10.99)
S 1821
Power supply AC types
Rated operational voltage
Through pins 2 & 10
024
24 VAC 15%, 45 to 65 Hz
115
115 VAC 15%, 45 to 65 Hz
230
230 VAC 15%, 45 to 65 Hz
Voltage interruption
40 ms
Dielectric voltage
2 kVAC rms) (supply/elect.)
Rated impulse withstand volt.
4 kV (1.2/50 s) (line/neutral,
line/line), direct connection
to electronics
Rated operational power
2.5 VA
Delay on operate
0.2 - 10 sec
Reaction time
= 100 ms, worst case reac-
tion time may be up to 5 x
Indication for
Power supply ON
LED, green
Output ON
LED, red
Environment
(IEC 60947-1)
Degree of protection
IP 20 B (IEC 60529)
Pollution degree
2 (IEC 60664)
Operating temperature
-20 to +50C (-4 to +122F)
Storage temperature
-50 to +85C (-58 to +185F)
Weight
200 g
Approval
UL, CSA
Mode of Operation
The relay measures average
power, U x cos
, up to maxi-
mum 125 kW, and at the same
time works as a power direc-
tion relay, whereby the relay is
suitable for power measuring
with wind driven generators
(windmills).
The relay is used with current
metering transformers type MI
100 or MI 500. The S 1821
measures on its own power
supply and has a built-in adju-
stable delay on operate of 0.2
- 10 secs. If higher metering
sensitivity is required, the me-
tered cable can be put through
the current metering transfor-
mer several times.
Example 1
The S 1821 measures the
power on one phase; at sym-
metrical load this one is re-
presentative of all three pha-
ses. When the registered av-
erage power exceeds the set
power level, the relay oper-
ates with a delay 0.2 - 10
secs. The relay releases im-
mediately, when the measured
average power drops below
the set value minus the hy-
steresis.
Example 2
S 1821 is used with a genera-
tor connected to the mains.
The relay measures the aver-
age power supplied from the
generator.
The value of the average
power is read out on the con-
nected instrument. At wrong
direction the instrument dis-
plays zero. The relay is appli-
cable for coupling in , e.g. a
heating element, in order to
avoid transmission of power
to the mains. Step-by-step
coupling in/out of heating ele-
ments is possible by up to 5
relays type S 178 connected
to S 1821. In this connection
the S 178's works as power
metering relay, as the current
supplied from the S 1821 is
proportional to the average
power.
Note: Pin 7 is connected in-
ternally to pin 10 (neutral) and
pin 9 must not be externally
connected.
Wiring Diagrams
Example 1
Example 2
Power supply
PE = Pin 7
Generator
S 178
Load < cos
Load < cos
S 1821
Supply Specifications
General Specifications
Specifications are subject to change without notice (27.10.99)
3
S 1821
Time/Range Setting
Time setting
Upper potentiometer:
Delay on operate:
0.2 to 10 s (tolerance on
max.: -1 s, +3 s).
Range setting
Lower potentiometer:
Level of average power on
scale from 10 to 100%.
Sockets
D 411 B, S 411
Hold down spring
HF
Mounting rack
SM 13
Socket covers
BB 4, BB 5B
Front mounting bezel
FRS 2
Current metering transformers MI 100, MI 500
Potentiometer lock
PL 2
For further information refer to "Current Metering Transfor-
mers" and "Accessories".
Accessories
Hysteresis
Approx. 10% in the upper
range and approx. 30% in the
lower range.
Operation Diagrams
Power supply
Set value
Relay ON
Example 1
Example 2
Hysteresis
Effective power
Power supply
Set value
Relay ON
Hysteresis
Effective power
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