Electrical Installation Safety Trainer
AD 1 - MI 3399
85
values. The calculated result U
CSF1
returns the expected contact voltage in a single
fault.
Typical measurements & calculations:
I
SFL1
, I
SFL2
, I
SFL3
for individual or group earthing
U
CSF1
, U
CSF2
, U
CSF3
(calculated) for each individual or group earthing
The earthing resistances of individual and group earthings must be known for the U
CSF
calculation:
𝑈
𝐶𝑆𝐹𝑥
< (𝑅
𝐸
𝐿𝑂𝐶𝐴𝐿
+ 𝑅
𝑃𝐸𝐶
𝐿𝑂𝐶𝐴𝐿
) ∙ 𝐼
𝑆𝐹𝐿𝑥
= 50 (25) V
where:
U
CSF
– Contact voltages at single fault on earthing (calculated).
I
SFL
– Single fault leakage current (measured).
R
E_LOCAL
– Earthing resistance of each individual or group earthing
(measured).
R
PEC_LOCAL
– PE conductor resistance of each individual or group earthing
(measured).
2.5.1.2 Insulation monitor device (IMD)
IMDs and other monitoring devices usually include a self-test option for an alarm circuit.
The alarm circuit can be double checked by applying an adjustable resistor between
line and PE conductors.
When measuring IMD in an IT earthing system, we can either measure the response
of the IMD based by lowering resistance or the current in the circuit. In either case, the
allowed IMD values are:
30 k
Ω
≤
R
MEASURED
≤
50 k
Ω
I
MEASURED
≤
4,4 mA
All measured values in between these limits will not cause the IMD to sound the alarm.
All measured values that fall out of these barriers should produce an error.
2.5.2 Exercises
2.5.2.1 Exercise No. 2.5-1: Measuring single fault leakage currents
(I
SFL
)
Measuring procedure
1
To measure the single fault leakage currents select first the
I
SFL
function in the
Other
section.
2
Set the maximum allowed short circuit current on both lines by clicking in the
bottom left dark grey corner.
Summary of Contents for MI 3399
Page 27: ...Electrical Installation Safety Trainer AD 1 MI 3399 27...
Page 46: ...Electrical Installation Safety Trainer AD 1 MI 3399 46 3 Exit settings...
Page 74: ...Electrical Installation Safety Trainer AD 1 MI 3399 74...
Page 197: ...Power and Voltage Quality Trainer AD 2 MI 3399 197 Figure 4 89 Transient Chart view...
Page 204: ...PAT Appliances Machines Safety Trainer AD 3 MI 3399 204...
Page 249: ...PV Photovoltaic Systems Trainer AD 4 MI 3399 249...
Page 250: ...PV Photovoltaic Systems Trainer AD 4 MI 3399 250 AD 4 MI 3399 PV Photovoltaic Systems Trainer...
