VRE-11A Single Channel Monitoring Unit

USA model
 VRE-11US
English
Other countries
 VRE-11AE
VRE-11AS
VRE-11A
English
Swedish
Finnish

VRE-11A Measuring range 1 mA to 10 A. Alarm setting 10 mA to 10 A.
VRE11A / 100 Measuring range 10 mA to 100 A. Alarm setting 100 mA to 100 A.

VRE-11P Portable model
VRE-11P / 100 Portable model

Sum Current Transformers
Inner diameter from 1" (25 mm) to 8" (200 mm)
Window type Sum Current Transformers max H = 10" (250 mm)
and max length L = 26" (660 mm)


The VRE-11A is a microprocessor-based Ground Fault on-line monitoring unit for a single point monitoring in a grounded electrical power system. The supervision unit is used with sum current transformer by a measuring cable.

The main specifications are:

  • Display of the absolute value of the fault current in the range 1 mA to 10 A
  • All settings are done by three buttons: neither reference current sources nor calibration of the operation point are needed
  • Memory for the maximum and minimum value of the measured current
  • Relay contacts: two separate single pole, double throw dry contacts 230 V 5 A
  • Continuous self testing: confidence and operation reliability
  • Panel installation
  • AC-analog-output, recorder or data logger use

FEATURES OF VRE-11A

  • DIGITAL DISPLAY OF FAULT CURRENT FROM 1mA to 10A
  • EASY SETTINGS WITH DIGITAL DISPLAY
  • MEASURING DISTANCE UP TO 320 FT (100 m)
  • SELF TESTING
  • MIN AND MAX MEMORY


APPLICATIONS OF SUPERVISION UNIT VRE-11A

Supervision of a grounded (3-phases+N+G / 3-phases+G / 1-phase+N+G) distribution power system

In a grounded distribution system the return current flows through the neutral conductor (N) back to the main ground bus. The current in the grounding (G) conductor is theoretically zero. However, in practice there is a small current in the G conductor the so called inherent leakage current. It is caused by different devices, filters and big fluorescent lamp groups connected to the electrical system. This leakage current increases if faults occur in the distribution system from insulation damages in the devices connected to the distribution system or from wiring errors in the electrical system itself. These faults may appear as faults or short circuits between the ground conductor and the power supply. It is important to detect an emerging fault and remove it quickly in order to guarantee the proper operation of the grounded electrical system. A continuous fault situation may be hazardous for the user, for the equipment connected to the electrical system as well as to the system itself (overheating arcing faults and fire risk).

Supervision of the integrity of a distribution network

Leakage and stray currents cause potential differences and disturbance voltages in computer and building management networks. These power disturbances are particularly harmful in data lines. If a partial or complete short circuit occurs between the N and G conductors, the electrical system operates as a four conductor system. In this case the benefits of a five conductor system are lost. Only by continuous supervision of a grounded electrical system can be kept "clean".

Detection of wiring errors

Wiring errors may spoil the advantages of a grounded electrical system from being achieved and cause hazards for the user. With the help of a supervision unit the wiring errors may be detected immediately. Possible wiring errors are:

  • N and G conductors are connected together not only through the main ground bus
  • N and G conductors have been reversed somewhere in the electrical system
  • a device has been connected between a phase conductor and the ground
  • a device is grounded through its installation parts.
  • Neutral to neutral wiring errors (if the measurement is close to the load)

Detection of insulation deterioration

The most usual reason for a fire risk of an electrical device (cable, motors, heating systems etc.) is the damage in the cable insulation. This may occur due to overloading, excessive moisture, insulation deterioration, mechanical stress, etc. The supervision equipment detects an incipient insulation damage as the fault current value rises. The Superintend system detects an arcing fault before a fuse or a circuit breaker operates.

Measurement of small currents

With this supervision unit it is possible to measure small currents in the range of 1 mA to 10 A

On-line monitoring of electrical insulation

Over time leakage current increases because the insulation begins to degrade. By continuous monitoring of leakage current, weakened insulation can be identified before the circuit breaker trips and production is shut down.


MONITORING WITH A RECORDER

AC output for a recorder
1mVAC = 1mAAC
VRE-11 reading 1mA-2.5A
VRE-11/100 reading 10mA-25A

ANALOG OUTPUT

Voltage output in the range 10mA-10A
The thick line corresponds the analog output voltage measures in the VRE-11A.
A linear voltage output is gained when the current is below 2.5A.


DISPLAY
DISPLAY EXAMPLES
Measuring normal display. Continuous measuring.
Range selection mA/A works automatically.
Display indicates 290 mA
Measuring range is 5 mA to 9.99 A.
SETTINGS
MODEL SETUP RANGE STEP
VRE-11A 10-100 mA 10 mA
100 mA 25 mA
1.00-9.75 A 250 mA
VRE-11A / 100 10 A-97.5. A 2.5 A
SETUP RANGE STEP(S)
0-10
10-60		 1
5
SELF TESTING


VRE-11A tests itself automatically every 90 seconds.
Fault indication: power break (shown on the display)
or
Fault indication: low test current.
The fault could be e.g. loss of measuring wire.
ALARM DISPLAY
Alarm limit has been exceeded.
The duration of the alarm has been shorter than the set delay.
Current alarm.
The duration of the alarm has been longer than the set delay.
Equipment fault.
The faults can be scrolled in the fault record.
MIN/MAX CURRENT MEMORY
Display of max current (491mA).
Display of min current (97mA).
Max/min current memories can be reset. Active equipment faults stay in memory until the fault has been fixed and acknowledged.


AN EXAMPLE OF WIRING


CONNECTIONS OF VRE-11A



Terminal connections of Superintend VRE-11A


INTERCONNECTION CABLES

WIRING WITH STANDARD PLUG-IN MEASURING CABLES:

IN THE USA 600 V, 90°C
IN THE OTHER COUNTRIES 1000 V, 90°C


WIRING WITH INSTRUMENTATION CABLE

Installation with screw terminals

The VMPH-2F measuring cable for the current transformer is 2-feet long (0.6 m). One end of the cable has a plug connector (for VRE-11A unit) and the other end has four colour-coded wires for connection to screw terminals on the instrumentation cable.

Installation with plug-in measuring cables

The VMP-2F measuring cable for the current transformer is also two-feet long (0.6 m). Both ends of the cable have plug connectors. The VMPA-1 (one channel model) and VMPA-4 (four channel model) are adapters for VMP-2F measuring cable. The adapter has socket(s) for VMP-2F measuring cable and screw terminal(s) for the instrumentation cable.


TECHNICAL SUMMARY

Leakage Current Monitor VRE-11A
Operating voltage
USA 110...120VAC 60Hz
Other countries 230V + 10% 50 Hz
Power consumption
1.5VA
Operating temperature
+22...+122°F (-5...+50°C)
Humidity
< 95%, non condensed
Dimensions
shown on the next page
Installation
mains and the alarm relay
screwterminal
sum current transformer
4-pin modular connector
voltage output
Ø 0,16" (4 mm) socket (front panel)
Weight
VRE-11A 1 lb (450 g)

Measuring characteristics
Channel 1 pc
Measuring range
VRE-11A
0 - 9.99A (60Hz)
VRE-11A/100
0 – 99.9 A
Resolution
VRE-11A
- I < 1A 1mA
- I 1A
VRE-11A/100
-I < 10A 10 mA
-I > 10A 100 mA
Accuracy with
VMI
+5% (closed core), + 1-2 dgt
VMIK
+10% (split-core) , + 1-2 dgt
Setup
alarm range
VRE-11A
VRE-11A/100
10 mA - 9.5A
100 mA – 95 A
alarm delay
0 - 60 s (with the minimum
delay the action time of the relay is 140 ms)
hysteresis

0 - 90% alarm level
AC-output
VRE-11A
correspondence
1mVAC = 1mAAC

linear measuring range
1 mA - 2.5 A

accuracy:
+ 5% with the VMI transformers
+10% with the VMIK transformers
VRE-11A/100
correspondence
1mVAC = 1mAAC

linear measuring range
10 mA - 2.5 A

accuracy:
+ 5% with the VMI transformers
+ 10% with the VMIK transformers


Alarm relay
relay connection
two potential free, change-over contactors
Imax
max. 5A
Vmax
250 V AC
Vmax
24 V DC
Current transformer
thermal limit current Ith/t
20kA/s
dynamic limit current Idyn
50kA
continuous thermal limit current
100A


DIMENSIONS