Pulse Generator
| Intro |
Description | Measuring Circuits
| | Dimensions &
Weights | Accessory |
GENERAL
The quantities measured in partial discharge tests must
be multiplied with a correction factor in order that test results
obtained from a specific test object will be reproducible in
different test circuits. This correction factor must allow for the
circuit characteristics.
The pulse generator PDG has been designed to produce
uniform and reproducible pulses by which the correction
factor can be determined as under;
Correction factor K =
Where
CP is the test object capacitance
CR is the sum of all capacitance in the high voltage circuit (internal capacitance of test
transformer, capacitance of the measuring capacitor and stray
capacitance to ground)
DESCRIPTION
The battery-operated pulsegenerator PDG produces
pulses of constant amplitude and constant electrical
charging content. These pulses appear at a repetition
frequency equal to twice the mains frequency.
A photocell in the pulse generator is excited by the lighting equipment and synchronizes the repetition
frequency of the generated pulses. It is, therefore, important
that the pulse generator is position such that light from
artifical sources will strike the photocell. The battery charge is
indicated with an LED when the button "CHECK" is pressed.
The following output terminals are provided: 5-50-500-5000
pC.
The impulse front time is approx. 50 nS.
MEASURING PRINCIPLE
For partial discharge measurements according to IEC publ. 60270 and IS 6209 with partial discharge meter
DTM,
the pulse generator is connected to the deenergised test
circuit in parallel with the test object (Fig.1). Care should be
taken to use the shortest possible leads.
The corrections factor shall be determined according to Fig. 2 if (a) another type of partial discharge meter is used
(b) the correction factor shall be determined according to
VDE 0434.
DIMENSIONS AND WEIGHT
30 × 130 × 110 MM
650 grams
ACCESSORY
9 Volt battery.
Measuring Circuits
Fig. 1
Determination of the correction factor for partial discharge measurement
Connection of PDG between “A” and “B” (50 pC terminal)
Switch on filter of DTM to “CORR”
Direct reading of Correction factor on “CORR” scale
Fig. 2
Determination of the correction factor for partial discharge measurement
acc. to VDE 0434.
a) Connection of PDG to define
a1
a) Connection of PDG to define a2
Determination of the correction factor :
a1
a2
TEO = Test transformer
CM = Measuring capacitor
CK = 1000 pF Coupling capacitor
P = Test object
DTM = Partial discharge meter
AKV = Coupling quadripole
PDG = Pulse generator
