info@amperis.com (+34) 982 20 99 20
The AHM35 and AHM45 are designed to be the most reliable 35 and 45kV testers available. They can be used for most Industrial and Substation testing including insulation resistance, dielectric absorption, DC hipot and polarization index tests. Units can be operated off of 120V AC or 12V DC with the optional inverter and a light, easily portable design makes no job site too remote.
THEORY:
The capacitive discharge system is the most universally accepted way to locate underground cable faults. It is still the only system that works reliably on shielded cable such as URD type concentric neutral cable.
The basic capacitor discharge system consists of a capacitor, a high voltage D.C. power supply, and a means of connecting and disconnecting the capacitor to the center conductor of the faulted cable such as an impulse control gap. These components are shown in the simplified diagram below. The fault is shown as a gap. This is an accurate description of faults on URD type cable since a fault is a hole or cut in the insulation between the center conductor and the grounded semiconductor, shield wires and earth. The objective of the system is to dump the stored electrical energy in the impulse capacitor into the cable fault such that an audible noise or thump is made. The thump should be loud enough to be heard and felt by personnel without detectors walking above the cable.
The amount of energy available at the fault to "thump" the ground or ductwork is related to the characteristics of the fault gap, the electrical impedance of the path from the discharge capacitor to the fault and back, the energy in the discharge, the voltage of the discharge, and the rise time of the discharge. A fast rise time provides maximum noise at the fault with the least energy. After each discharge, the power supply must charge the capacitor bank. The variable autotransformer on the power supply is used to adjust the rate of discharge. Amperis systems are designed for a continuous rate of discharge every six seconds at 30kv. The discharge voltage of the capacitor is related to the impulse control gap voltage and the fault gap voltage since they are in series. By adjusting the impulse control gap, the impulse capacitor can be charged to its rated voltage regardless of the characteristics of the fault gap. This allows the fault to be located with minimum energy and voltage. To locate a fault the voltage rating of the discharge capacitor must exceed the voltage rating of the fault gap. The 35kv maximum discharge voltage has proven to be sufficient for all presently installed solid dielectric distribution cable.
THE MEGOHM SCALE:
Megohms are listed above both the 0-10 and 0-30 scales on the output current meter. To measure megohms resistance with minimum calculation, set the output voltage precisely on a value selected from the chart. Turn the output current range switch to the lowest range or until the output meter reads in the middle or the right third of its scale. Record the megohm reading just above the current scale used and multiply this by the multiplier found on the cart for megohms resistance. As a check, the minimum, center scale, and maximum resistance readings are listed for each range setting.
SAMPLE OF CHART:
Voltage test |
Switch setting |
Upper scale |
Lower scale |
Maximum ohms |
Center ohms |
Minimum ohms |
1000V |
10 mA |
.1 |
|
10 MEG |
200 |
100 |
3 mA |
|
.1 |
40 MEG |
666 |
333 |
|
1 mA |
1 |
|
100 MEG |
2 MEG |
1 MEG |
|
300 mic |
|
1 |
400 MEG |
6,66 MEG |
3,33 MEG |
|
100 mic |
10 |
|
1000 MEG |
20 MEG |
10 MEG |
|
30 mic |
|
10 |
4000 MEG |
66,6 MEG |
33,3 MEG |
|
10 mic |
100 |
|
10000 MEG |
200 MEG |
100 MEG |
The AHM35 and AHM45 portable unit contains:
Specifications:
Weight |
AHM45: 115 pounds (52.3 kg) // AHM35: 80 pounds (36.4 kg) |
Width |
15.125" (38.5 cm) |
Height |
AHM45: 24.5" (62.3 cm) ) // AHM35: 18" (45.7 cm) |
Length |
23" (58.4 cm) over handles |
Input |
110-125 volts 50-400 Hz A.C. |
Impulse |
6 nanosecond rise time, |
Testing |
6 ma to 35kv, 1% ripple |
Case |
Aluminum with grey finish |
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Do not hesitate to contact us, call us today by phone (+34) 982 20 99 20. We are happy to help you.