Analyzing the partial discharge activity requires the permanent installation of coupling devices. Preferably, such coupling devices are capacitive couplers terminated by a power separation filter.
The coupling device in a PD measuring circuit allows sensing the partial discharge pulse and sending it as a voltage signal to a preamplifier for conditioning.
Il dispositivo di accoppiamento in un circuito di misura di Scariche Parziali fornisce il mezzo per la rilevazione dell'impulso PD, e per l'invio dello stesso sotto forma di segnale in tensione a un preamplificatore per l'opportuno condizionamento.
Power Diagnostix standard coupling capacitors are mounted on sturdy cast aluminum enclosures. They can be used for online and offline measurements on rotating machines and various smaller test setups. A wider range of coupling capacitors and capacitor assemblies complete with quadrupoles and preamplifiers is available on request. The table to the right lists some standard models of coupling capacitors provided by Power Diagnostix, along with their built-in circuits, if present.
| Type | Capacitance | Nom. Voltage [kV] | Built-in Quadrupole | Built-in Voltage Divider | Built-in RF CT | Max. Height [mm] |
| CC7B | 440 pF | 7 | Yes | Yes | 152 | |
| CC14B | 220 pF | 14 | Yes | Yes | 190 | |
| CC20B | 145 pF | 21 | Yes | Yes | 300 | |
| CC25B | 1 nF | 25 | Yes | Yes | 300 | |
| CC25B/V | 1 nF | 25 | Yes | Yes | 300 | |
| CC25C/V | 1 nF | 25 | Yes | Yes | Yes | 300 |
| CC35B/V | 145 pF | 35 | Yes | Yes | 310 | |
| CC50B/V | 1 nF | 50 | Yes | Yes | 500 | |
| CC50C/V | 1 nF | 50 | Yes | Yes | Yes | 500 |
| CC100B/V | 1 nF | 100 | Yes | Yes | 695 | |
| CC150B/V | 1 nF | 150 | Yes | Yes | 1210 | |
| CC200B/V | 0.5 nF | 200 | Yes | Yes | 1300 | |
| CC300B/V | 0.5 nF | 300 | Yes | Yes | 2425 |
Coupler Termination Boxes
Coupler capacitor units are usually connected to a coupler termination box (CTB). A coupler termination box is necessary for providing the protective ground for the coupler's BNC signal cable.
| Type | Channels | Spark gap | Input | Output |
| CTB1A | 3x | 350 V | BNC | BNC |
| CTB1C | 3x | 350 V | TNC | BNC |
| CTB2A | 4x | 350 V | BNC | BNC |
| CTB2C | 4x | 350 V | TNC | BNC |
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