The function can be enabled and disabled with the Operation setting. The corresponding parameter values are "On" and "Off".
The operation of PHPTOV can be described using a module diagram. All the modules in the diagram are explained in the next sections.
Level detector
The fundamental frequency component of the measured three-phase voltages are compared phase-wise to the set value of the Start value setting. If the measured value is higher than the set value of the Start value setting, the level detector enables the phase selection logic module. The Relative hysteresis setting can be used for preventing unnecessary oscillations if the input signal slightly differs from the Start value setting. After leaving the hysteresis area, the start condition has to be fulfilled again and it is not sufficient for the signal to only return to the hysteresis area.
The Voltage selection setting is used for selecting phase-to-earth or phase-to-phase voltages for protection.
Phase selection logic
If the fault criteria are fulfilled in the level detector, the phase selection logic detects the phase or phases in which the fault level is detected. If the number of faulty phases match with the set Num of start phases, the phase selection logic activates the Timer.
Timer
When the operation timer has reached the value set by Operate delay time in the DT mode or the maximum value defined by the IDMT, the OPERATE output is activated.
When the user-programmable IDMT curve is selected, the operate time characteristics are defined by the parameters Curve parameter A, Curve parameter B, Curve parameter C, Curve parameter D and Curve parameter E.
If a drop-off situation occurs, that is, a fault suddenly disappears before the operate delay is exceeded, the reset state is activated. The behavior in the drop-off situation depends on the selected operate time characteristics. If the DT characteristics are selected, the reset timer runs until the set Reset delay time value is exceeded. If the drop-off situation exceeds the set Reset delay time, the Timer is reset and the START output is deactivated.
When the IDMT operate time curve is selected, the functionality of the Timer in the drop-off state depends on the combination of the Type of reset curve, Type of time reset and Reset delay time settings.
| Reset functionality | Setting Type of reset curve | Setting Type of time reset | Setting Reset delay time | |
|---|---|---|---|---|
| Instantaneous reset | Operation timer is “Reset instantaneously” when drop-off occurs | “Immediate” | Setting has no effect | Setting has no effect |
| Frozen timer | Operation timer is frozen during drop-off | “Def time reset” | “Freeze Op timer” | Operate timer is reset after the setReset delay time has elapsed |
| Linear decrease | Operation timer value linearly decreases during the drop-off situation | “Def time reset” | “Decrease Op timer” | Operate timer is reset after the set Reset delay time has elapsed |
The Time multiplier setting is used for scaling the IDMT operate times.
The Timer calculates the start duration value START_DUR, which indicates the percentage ratio of the start situation and the set operation time. The value is available in the Monitored data view.
Blocking logic
There are three operation modes in the blocking function. The operation modes are controlled by the BLOCK input and the global setting in which selects the blocking mode. The BLOCK input can be controlled by a binary input, a horizontal communication input or an internal signal of the protection relay's program. The influence of the BLOCK input signal activation is preselected with the global Blocking mode setting.