Alarm event records

Each event is stored using two records:

  • A "primary" record, which is created when the insulation alarm or preventive insulation alarm occurs. This contains the insulation value.

  • A "secondary" record, which is created for the following type of events:

    • Acknowledged insulation alarm

    • Transient insulation alarm

    • Power failure or power cycle

    • Product error

    • Injection disable

    • Over capacitance

    • Over voltage

    NOTE: The listed secondary records are applicable for insulation alarm and preventive insulation alarm.

Description of an Event Record in the Log

Register Unit Type Range Description
Word 1 Uint16 1...65535 Event record number

Word 2

Word 3

Word 4

Word 5

Uint64 Time tagging of event (using the same code as for the product date/time)

Word 6

Word 7


  • 0x00….0xFF

  • 0x40, 0x20

  • 1020...1021, 1110

Record identifier:

  • Word 6, most significant byte: information for primary/secondary record. This field identifies the type of primary and secondary record.

  • Word 6, least significant byte: type of data stored in the Value field.

  • Word 7: address of the Modbus register that is the source of the data in the Value field.

Word 8

Word 9

Word 10

Word 11


Depending on the type of record (primary or secondary):

  • Primary record (when the event occurs): Insulation resistance value (in Ohm) when the event occurred (encoded in Float32 in the last 2 registers).

  • Secondary record (for the earlier list of events) (encoded in Uint32 in the last 2 registers)

Word 12 Uint16 1...65534

Primary/secondary record identifier for the event:

  • In the case of a primary record for an event, this identifier is an odd integer; numbering starts at 1 and the number is incremented by 2 for each new event.

  • In the case of a secondary record for an event, this identifier is equal to the primary record identifier plus 1.

For the Word 6 (most significant bytes), the ranges are 0x00….0xFF. The assigned bytes for the primary and secondary events are listed as follows:

Event Byte
Primary events
Preventive insulation alarm 0x01
Insulation alarm 0x02
Secondary events
Nominal 0x21
Transient insulation alarm 0x22
Acknowledged insulation alarm 0x23
Injection disabled 0x24
Over capacitance 0x25
Over voltage 0x26
Product error 0x27
Power failure or power cycle 0x28
Preventive Nominal 0x41
Preventive transient insulation alarm 0x42
Preventive acknowledged insulation alarm 0x43
Preventive injection disabled 0x44
Preventive over capacitance 0x45
Preventive over voltage 0x46
Preventive product error 0x47
Preventive power failure or power cycle 0x48

Example of an event

The next 2 records relate to an example insulation alarm that occurred on October 1, 2010 at 12:00 pm and was acknowledged at 12:29 pm.

Record number: 1

Address Register Unit Type Value Description
dec hex dec hex
20002 4E22 20003 4E23 Uint16 1 Record number
20003 4E23 20004 4E24 Uint64

  • 10

  • 0

  • 10

  • 1

  • 12

  • 0

  • 0

Date when insulation alarm occurred (October 1, 2010, 12:00 pm)
20007 4E27 20008 4E28 Uint32

  • 0x02

  • 0x40

  • 1020

Record identifier:

  • Primary record plus secondary record

  • Float32 value (insulation resistance)

  • Value of register 1020 (register for insulation resistance monitoring)

20009 4E29 20010 4E2A Ohm Uint64 10000 Insulation resistance value at the time of the insulation alarm
20013 4E2D 20014 4E2E Uint16 1 Secondary record identifier for the event

Record number: 2

Address Register Unit Type Value Description
dec hex dec hex
20014 4E2E 20015 4E2F Uint16 2 Record number
20015 4E2F 20016 4E30 Uint64

  • 10

  • 0

  • 10

  • 1

  • 12

  • 29

  • 0

Date when insulation alarm acknowledged (October 1, 2010, 12:29 pm)
20019 4E33 20020 4E34 Uint32

  • 0x23

  • 0x20

  • 1110

Record identifier:

  • Secondary record

  • Uint32 value (alarm acknowledged)

  • 1110 register value ( product status register).

20021 4E35 20022 4E36 Uint64 8 Value of insulation alarm register at the time of insulation alarm acknowledgement
20025 4E39 20026 4E3A Uint16 2 Secondary record identifier for the event
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