 | |
| Illustration 1 | g00481725 |
Functional Block Diagram Of AC Voltage Display in EMCP II | |
| AC Voltage Range Selection | ||||
|---|---|---|---|---|
| GSC P20 Setpoint | External Potential Transformer | AC Transformer Box (ATB) Input Voltage Range | GSC Internal Multiplier | Jumper |
| 700 | None | 0 - 700 | 5 | Required |
| 150 | None | 0 - 150 | 1 | None |
| 300 | 2:1 | 0 - 150 | 2 | None |
| 500 | 3.33:1 | 0 - 150 | 3.33 | None |
| 600 | 4:1 | 0 - 150 | 4 | None |
| 750 | 5:1 | 0 - 150 | 5 | None |
| 3000 | 20:1 | 0 - 150 | 20 | None |
| 4500 | 30:1 | 0 - 150 | 30 | None |
| 5250 | 35:1 | 0 - 150 | 35 | None |
| 9000 | 60:1 | 0 - 150 | 60 | None |
| 15000 | 100:1 | 0 - 150 | 100 | None |
| 18000 | 120:1 | 0 - 150 | 120 | None |
| 30000 | 200:1 | 0 - 150 | 200 | None |
The AC voltage and/or current values are inaccurate.
Note: For related information, see Testing And Adjusting, "AC Voltage Range - Adjust"
The P20 setpoint determines the proper AC voltage range and the internal multiplier that are used by the GSC for calculating AC voltage. The GSC uses the internal multiplier to compensate for the turns ratio of the external potential transformers (if present). The turns ratio of the external potential transformer must match the internal multiplier in order to ensure an accurate AC voltage calculation by the GSC.
The jumper block is located in the relay module. The jumper block connects a "divide-by-five circuit" to the AC voltage input of the GSC. The "divide-by-five circuit" reduces the AC voltage input to a controllable level for the GSC when P20 is 700. When setpoint P20 is 700, a multiplier of five is needed to compensate for the presence of the "divide-by-five circuit". This is done even though no external potential transformer is present.
Note: In order to prevent an inaccurate voltage calculation by the GSC, the jumper block should NOT be installed when P20 is programmed to a value that is different from 700. The other values (150 through 30 000) are used with an external potential transformer. The values result in input voltages from 0 to 150 ACV at the AC Transformer Box (ATB). No further reduction of the input voltage is required.
Do the following procedure to determine the cause of inaccurate AC voltage and/or current values on the GSC.
- Check setpoints P20 (full scale voltage) and P21 (full scale current). In order for the GSC to operate correctly, the current transformers (CT) must have 5 amp secondaries. See Testing And Adjusting, "Engine/Generator Setpoint Viewing OP2" and Testing And Adjusting, "Engine/Generator Programming OP5". Typical factory setpoints are as follows: 700 V for P20 and 600 A for P21. The setpoints should be correct for the generator set application.
- Refer table 1 and illustration 1 in order to help determine the proper setpoints and any necessary external potential transformers.
- If only the voltage is inaccurate, check the jumper for the AC voltage range for correct installation. The jumper should be installed for systems with a full scale AC voltage input of 700 volts (P20 = 700). The jumper should NOT be installed for systems with 150 volt full scale AC inputs. Also, the jumper should be NOT installed for any unit with external potential transformers. For information regarding the installation of the jumper, see Testing And Adjusting, "AC Voltage Range - Adjust".
- Check Systems Operation, "Voltmeter/Ammeter Programming OP8". OP8 is the option for programming the calibration value of the voltmeter and the ammeter. The calibration values, written on the ATB bar code sticker, must be programmed into the GSC to ensure accurate voltage and current values.
- Check the AC offset adjustment. See Systems Operation, "AC Offset Adjustment OP10". If necessary, set the voltage offsets to 0%.
Note: The adjusted voltages are for display only. The adjusted voltages will NOT be transmitted over the CAT data link to other modules (such as the Customer Communication Module). Also, the adjusted voltages are NOT used for determining the fault thresholds for protective relaying functions. In both cases, the values that are not adjusted for AC voltage are still determined by the GSC. These values will be used instead of the displayed values.
 | |
| Illustration 2 | g00481733 |
Polarity Of Current Transformers | |
Note: If the readings of the power meter on the GSC are inaccurate, check the power factor. Also check the power for each individual phase. Hold the power meter key for more than five seconds. If the readings for any individual phase are inaccurate, check the polarity of the current transformers (CT) in the generator housing. If the polarity of the current transformers is correct, replace the ATB.