# Damped high-pass harmonic filter

Canonical URL: https://eloragrid.ai/symbols/damped-high-pass-harmonic-filter
Publisher: Elora Grid
Updated: 2026-10-28
Lookup label: HPF
Drawing use: SLD, Schematic
Reference families: IEC, IEEE / ANSI

A shunt filter with a resistor across its reactor, giving low impedance over a broad band of higher harmonics.

## In plain English

### What does Damped high-pass harmonic filter mean?

A damped high-pass filter adds a resistor in parallel with the reactor of a capacitor-reactor branch. Above its corner frequency the filter impedance stays low across a wide band, so it absorbs higher-order harmonics and damps resonances rather than sinking one specific order. The C-type variant adds a second capacitor to remove fundamental-frequency losses in the resistor.

### A simple example

Drawings show the capacitor in series with a reactor that has a resistor in parallel, sometimes with the extra capacitor of the C-type arrangement in series with the reactor. It is used beside tuned filters in static var compensators, large rectifier plants and some converter connection points.

### What the drawings help you do

The resistor dissipates real power, so its thermal rating is as important as the electrical values. The symbol does not show the corner frequency or the loss figure, which come from the filter design report.

### This particular reference

A shunt filter with a resistor across its reactor, giving low impedance over a broad band of higher harmonics. A damped high-pass filter covers a band of harmonics; a single-tuned filter sinks one order and has no resistor branch.

### Terms

- Terminal: An identified point where a conductor connects.
- Rating: A value stating the conditions for which equipment is specified.
- Schematic: A drawing showing function and connections rather than physical appearance.

Concept diagram: Identify the device and form → Read the connections and state → Check the equipment reference
A guide to reading this reference. The original symbol illustration and its drawing notes appear below; these boxes are not a wiring diagram.

- [Capacitor and filter product offerings](https://www.hitachienergy.com/products-and-solutions/capacitors-and-filters)
- [Resistors and heater-element symbols](https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-1D071951-D38E-4B15-8B9E-C30ECBD55C19.htm)


## What it represents

A damped high-pass filter adds a resistor in parallel with the reactor of a capacitor-reactor branch. Above its corner frequency the filter impedance stays low across a wide band, so it absorbs higher-order harmonics and damps resonances rather than sinking one specific order. The C-type variant adds a second capacitor to remove fundamental-frequency losses in the resistor.
Drawings show the capacitor in series with a reactor that has a resistor in parallel, sometimes with the extra capacitor of the C-type arrangement in series with the reactor. It is used beside tuned filters in static var compensators, large rectifier plants and some converter connection points.
The resistor dissipates real power, so its thermal rating is as important as the electrical values. The symbol does not show the corner frequency or the loss figure, which come from the filter design report.

## How to read it

- A resistor across the reactor marks a damped filter.
- An extra series capacitor indicates a C-type arrangement.

## Information to show or reference

- State corner frequency, Mvar and resistor rating.
- Show resistor and capacitor arrangement.
- Reference filter design report.

## Important distinction

A damped high-pass filter covers a band of harmonics; a single-tuned filter sinks one order and has no resistor branch.

## Facts

- Elements: Capacitor, reactor, parallel resistor
- Response: Broad band above corner frequency
- Losses: Dissipated in resistor
- Preview: Independent educational illustration; consult the applicable standard and project legend for the exact graphic

## Public references

- [Capacitor and filter product offerings](https://www.hitachienergy.com/products-and-solutions/capacitors-and-filters) — Hitachi Energy. Public passive and harmonic filter product context.
- [Resistors and heater-element symbols](https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-1D071951-D38E-4B15-8B9E-C30ECBD55C19.htm) — Autodesk. Public resistor symbol family context.

## Graphic scope

Independent original educational concept illustration by Elora Grid. Not a certified standards graphic or manufacturer footprint. Unitless; not to scale. Original artwork licence: https://creativecommons.org/licenses/by/4.0/. Publisher material is linked only.