Option PT improves support for potential transformers (PTs), making it easier to use WattNode® for LonWorks® meters with medium voltage services. Specifically, Option PT adds a configuration property UCPTptRatio which configures the ratio of the external PT, allowing the meter to automatically scale the voltage, power, and energy readings.
Continental Control Systems (CCS) offers Option PT for the WattNode for LonWorks, Plus and Logger models. Option PT is not available with Option B or Option BI. It is still possible to use potential transformers with WattNode models that do not explicitly support PTs, but you must scale the same variables by the PT ratio to get the correct values.
Any WattNode for LonWorks (Plus or Logger) (but not Option B or BI models), may be ordered with Option PT by adding one of the following options to the model number.
This ensures that the WattNode model includes the special PT firmware version. The PT ratio will default to 1.0, which is the same as not using a PT. It will be necessary to set the PT ratio in the field using the UCPTptRatio configuration property. For example: WNC-3Y-208-FT10 Opt PT
This ensures that the WattNode model includes the special PT firmware version, and factory configures the PT ratio to nn. The PT ratio may be any value between 0.05 and 300. It is still possible to change the PT ratio in the field using the UCPTptRatio configuration property. For example: WNC-3Y-208-FT10 Opt PT=60
Common PT Ratios
|PT Primary Voltage|| PT Secondary Voltage
|Ratio = UCPTptRatio|
|840||120||840:120 = 7|
|1200||120||1200:120 = 10|
|2400||120||2400:120 = 20|
|4200||120||4200:120 = 35|
|4800||120||4800:120 = 40|
|7200||120||7200:120 = 60|
|8400||120||8400:120 = 70|
|12000||120||12000:120 = 100|
|14400||120||14400:120 = 120|
To fully take advantage of Option PT with LNS® based systems, you may want to use the following:
- XIF files
- LonWorks Resource Files – Version 1.05 is required
- LNS Plug-in for WattNode – Version 1.11 is required