Morgan Electro Ceramics has long experience of the manufacture of
ceramic capacitors for high voltage DC and power frequency
applications. These products are used all over the world in
onerous service conditions, and are backed by rigorous testing
procedures to ensure the electrical integrity and long service
life of such components.
Over one
million capacitors of the categories described here have been
successfully used in Live-Line Indication applications. Morgan
Electro Ceramics has decades of involvement in high voltage system
practices and the design of capacitors for those environments.
The
capacitors described in this section are used in circuitry
indicating the presence of voltage on conductors. A capacitor
voltage divider enables a small neon lamp to be illuminated or
alternatively the low voltage signal may be used to feed a sensing
circuit which monitors for supply failure and circuit condition .
Theory
In its simplest form the Live-Line Indication consists of a high
voltage ac rated capacitor which is connected in series with the
neon indicator between the phase and earth lines. (Fig.1) The
addition of higher value, low voltage rated capacitor in parallel
with the neon is sometimes preferred. (Fig.2) The object is
two-fold - firstly to advise the operator that the connections are
live and secondly for operation of re-routing systems in the event
of inadvertent disconnection.
Fig.1
Fig.2
C1
= High Voltage Series Capacitor
C2 =
low Voltage Shunt Capacitor
Material
Characteristics
Dielectric
Units
K1500
K2100
K3500
EIA
Category
Z5U
X7R
Y5U
Dielectric
Constant r
@ 1kHz, 20°C LV
approx
1500
approx
2100
approx
4300
Dielectric Constant r @
50Hz, 0.35kV/mm 20°C
approx 1650
approx 3000
approx 5200
Typical
Dissipation Factor @ 1kHz 20°C LV
%
=<0.5
=<2.0
=<1.0
Insulation
Resistance @ 500V, 20°C
ohm
>=1010
>=1010
>=1010
Ageing
Rate per decade hour
%
-3
-2.5
-3.5
Capacitors for encapsulation by the
user.
All Dimensions in mm
Style A
Style B
Style A
Type
Cap
Value
Cap
Tol
Dielectric
Voltage
rating
System
Voltage
Voltage
Test 1 Min
Voltage
Test Impulse
Discharge
Free Test
øD
L1
L2
Thread
Size Socket
pF
kV
rms
kV
kV
50Hz
kV
pk
kV<5pC
rms
mm
mm
mm
mm
07849
250
±20%
K3500
7
12
30
60
8
17
50.5
30.5
M4
07727
220
±20%
K3500
7
12
38
75
8
17
60
40
M4
07724
150
+20, -10%
K3500
15
24
55
140
26.4
17
81
61
M4
07723
50
±8pF
K1500
15
24
55
125
25.0
17
81
61
M4
07853
50
±10pF
K2100
15
24
55
125
26.4
12
81
61
M4
07897
20
±20%
K200
8
12
38
75
13.2
25
56
40
M4
07898
15
±20%
K200
15
24
50
125
26.4
25
82
62
M4
Style B
Type
Cap
Value
Cap
Tol
Dielectric
Voltage
rating
System
Voltage
Voltage
Test 1 Min
Voltage
Test Impulse
Discharge
Free Test
øD
L2
pF
kV
rms
kV
kV
50Hz
kV
pk
kV<5pC
rms
mm
mm
55530
150
+35, -15pF
K3500
14
24
55
140
15
17
61
55701
50
±10%
K1500
14
24
55
140
15
17
61
55559
50
±10%
K2100
14
24
55
140
15
12
61
Notes
1. Terminals are soldered to the ceramic parts with 220°C melting
point solder
2. Capacitors of this type have been used in transformer oil and
in SF6 gas. In these cases we would recommend a paint coating on
the otherwise bare ceramic surfaces.
3. The usual end product is a resin cast capacitor stand-off for
bus-bar or link support of appropriate height for the achievement
of the system requirements of flashover and creepage distance etc.
4. Additional metal connectors can be attached to the above on
request.
Capacitance Dividers
Many
users prefer to have Morgan Electro Ceramic supply in the
same moulding, not only the high voltage capacitor but also
a lower voltage capacitor of larger value. This shunts the
signalling circuit of the live-line indicator and prevents
the incidence of high voltage at the tapping point should
the indicating lamp loosen in the socket or become open
circuit.
In the
type of construction shown a heavily insulated HV lead is
taken from the capacitor at the top. The construction is
such that the lead contributes to a higher creepage distance
such that this range is useful for certain distribution
applications as well as for the requirements of mining
switchgear.
The
following descriptions apply to integral dividers primarily
designed for mining switch gear applications. However,
certain distribution switchgear requirements are met by
virtue of their electrical withstand properties.
Type
Cap
Value
Cap
Tol
Dielectric
Voltage
Rating
System
Voltage
(Distribution)
System
Voltage
(Mining)
Voltage
Test 1 Min
Voltage
Test Impulse
Discharge
Free Test
pF
%
kV
max
kV
kV
kV
50Hz
kV
50Hz
kV<5pC
rms
07529
375/5000
±10
K3500
4
3.6
7.2
20
40
5
07517
250/5000
±10
K3500
7
7.2
12
28
60
8
07590
250/5000
±10
K3500
7
12/17.5
38
95
8
07596
1000/5000
±10
K3500
4
3.6
7.2
10
40
5
07574
900/2500
±20
K3500
2
3.6
10
20
3
(Cap Value at 50Hz, +20°C)
Capacitors of Special Configuration
These
are shapes produced to meet special space limitation factors
and are often custom-made for the user.
r
@ 1kHz, 20°C LV
