Atec BM User Manual

BM11, BM11D, BM21 and BM25

5 kV Analogue/Digital Insulation Testers

BM11, BM11D, BM21 and BM25

5 kV Analogue/Digital Insulation Testers

n Spot tests and diagnostic insulation tests

n Simplicity and Ease of Use

n User safety features

n Unique rugged casing

n Analogue and Analogue/Digital Displays

n Wide range of test voltages

DESCRIPTION

The Megger® BM11 series of 5 kV Insulation Testers
provides a choice of features to suit all applications and
budgets.

The traditional BM11 instrument became the industry-
standard 5 kV tester. It is battery-powered, housed in a
rugged case and has a large, simple white-on-black scale.

The series has been extended with three analogue/
digital instruments; the BM11D, BM21 and BM25. These
instruments show results and test options on a large, clear
analogue/digital scale for both practicality and precision. A
built-in timer makes both spot tests and PI testing easier to
carry out.

They are powered by a built-in rechargeable lead-acid
battery which can be charged directly from any supply from
95 V to 265 V. All testers incorporate a guard terminal to
allow surface leakage to be removed.

Pre-set standard test voltages at 500 V, 1000 V, 2500 V and
5000 V are supplemented on the BM21 and BM25 units
with a variable test voltage in 25 V steps. These top of the
range units also allow measurement of resistance to 5 TΩ,
leakage current to 0,01 nA and can display capacitance at
the end of a test to 10 µF.

The BM25 extends the diagnostic testing capability of the
range by performing automatic Polarisation Index, Step
Voltage and Dielectric Discharge tests as well as providing
an optically isolated RS232 port for downloading results
during a test.

APPLICATIONS

The BM11 series is designed for testing the insulation of
high voltage electrical equipment and the wide voltage
range also allows it to be applied to low voltage
equipment.

Generators, motors, transformers, cables and switchgear all
require effective maintenance and the test techniques on
the Megger range give valuable diagnostic information.

‘Spot’ Insulation tests that are the most widely used, check
on the general condition of electrical insulation, called up
in most standards covering equipment design, testing,
installation and maintenance.

Insulation suffers from gradual steady decline, as well as
occasional sudden damage; the effects of dirt, grease,
moisture, vibration and chemical attack can be tracked
through the recording of Polarisation Index tests which
remove the temperature dependence of raw Insulation
Resistance measurements.

For finding more localised insulation problems, the BM25
includes both Step Voltage and Dielectric Discharge tests.
Step Voltage identifies local weak spots because they
respond differently as the electrical stress is increased,
while the Dielectric Discharge test can show up a single
bad layer in multilayer insulation.

The key to Predictive Maintenance is the trending of
diagnostic tests and this is facilitated on the BM25 by the
ability to use a PC to store results over time for trend
analysis.

BM11, BM11D, BM21 and BM25

5 kV Analogue/Digital Insulation Testers

FEATURES AND BENEFITS

All BM11 Series

n Choice of test voltages

n Direct reading display

n Unique rugged case

n Guard terminal

n Designed for user safety

BM11D

n Large, custom Analogue/Digital LCD

n Built-in timer

n Locking test leads for safety

n Battery indicator

n Automatic discharge of capacitance

n Voltage measurement and warning

n Tests to 500 GΩ

n Weather proof to IP54

BM11 BM11D

Features

n Large direct reading analogue scale n Large Analogue/digital display

n Guard terminal n Built-in timer
n Rugged case design n Locking test leads for safety
n 123 mm scale length n Battery indicator
n Weatherproof to IP54
Note: Not for sale in E.U. n Voltage measurement and warning

Test voltages (d.c.) 500, 1000, 2500, 5000 V 500, 1000, 2500, 5000 V

Accuracy (20°C) ±5% on open circuit ±5% on 100 MΩ load

Insulation 100 kΩ to 100 GΩ; at all test voltages Digital 10 kΩ to 50 GΩ @ 500 V
Resistance 10 kΩ to 100 GΩ @ 1000 V
Range 10 kΩ to 250 GΩ @ 2500 V
10 kΩ to 500 GΩ @ 5 kV
Analogue 100 kΩ to 1 TΩ @ all voltages

Basic Accuracy ±1,5% of arc length ±5% of reading 10 MΩ to 100 GΩ @ 5 kV

Short Circuit
Current 1 mA nominal, 2 mA max. 1,8 mA nominal, 2 mA max.

Voltage Range 50 to 1000 V d.c. or a.c. 50 to 1000 V d.c. or a.c.

Accuracy (20°C) ±5% ±10 V ±2% ±1 V

Display Analogue Analogue/digital (3 digits)

Interference
Rejection 2 mA a.c. (50/60 Hz) on 5 kV range 1 mA r.m.s. per kV to a maximum 2 mA

Capacitor
Discharge Time <1 s per µF to discharge from 5000 V to 50 V <2 s per µF to discharge from 5000 V to 50 V

Leakage current
measurement None None

Capacitance
measurement None None

Timer None Automatic; 0 to 60 minutes

Temperature Operating -15 to +55°C (5 to +131°F) Operating -20to +50°C (-4 to 122°F)
Range Storage -40 to +65 °C (-40 to +149°F) Storage -25 to +65 °C (-13 to +149°F)

Temperature
Coefficient < 0,04% of arc length per °C (0.2%/°F) (Applies over range 0 to 30°C) (32 to 86°F)
0,2% per °C (0.1%/°F) for test currents >100 nA 0,1% per °C to test voltage (0.05% per °F)

Humidity Range 90% RH @ 40°C max. (104°F) 90% RH @ 40°C max. (104°F)

Safety IEC348 IEC1010-1 (1995), EN61010 (1995) to installation
category III, 300 V, phase to earth, 500 V phase to phase