Tree Tech Model PI The Tree Tech Tap Position Indicator (PI) consists of a microprocessor based electronic device capable of monitoring and modifying, through the load tap changer (LTC), the positions of power transformer taps. The PI incorporates the functions of several equipment gears that were used in past times for controlling the transformers LTC, such as selector switches for Manual/Automatic and Local/Remote, manual control switch Raise/Lower and Tap Position Indicator, among others. For this reason, the command wiring and the number of components are greatly reduced, raising substantially the overall system reliability while reducing the installation and maintenance effort.

View PI Datasheet

Integrated serial communications using Modbus® RTU protocol makes it easy to incorporate the PI with other Tree Tech devices and/or third party products to create a comprehensive monitoring and control solution. For example, the PI module can be linked to the Tree Tech AVR module to create an Automatic Voltage Control system.

Like all Tree Tech devices, the PI is designed and thoroughly tested for operating in the most unfavorable conditions found in electric substations, including surges, impulses, electromagnetic interference and extreme temperatures.

Key Features

• Intelligent Tap Position Measurement:

  • Automatic compensation of the interconnection cable resistance between potentiometric position transmitter and PI, allowing longer distances with smaller cables (up to 600 meters with 1.5mm² conductors and 1000 meters with 2.5mm² conductors)

  • Detection and alarming of bad electrical contact in the potentiometric position transmitter or in the interconnection cables

• Indication of the LTC's position and type of tap position indication is user-selectable:

  • simple numeric (e.g. 1...33),

  • bilateral numeric (e.g. -8...0...+8), or

  • alphanumeric (e.g. 8L...N...8R)

• Number of positions set between 2 and 50

• Programmable resistance values meets all types of LTC

• Local/Remote selection made directly on the front panel or through external dry contacts.

• Manual/Automatic operation mode selection made directly on the front panel or through external dry contacts.

• Manual Raise/Lower commands made directly on the front panel or through external dry contacts.

• Current loop output enables the remote indication and/or monitoring of the LTC's position. Output range selectable by user at front panel (e.g. 0-1mA, 4-20mA)

• Four output relays to indicate status and/or alarms.

• All parameters can be configured through the PI's front panel or through the RS-485 communication port. All selections and commands can be performed also through the RS-485 data link.