Italy (TERNA) ride-through requirements
Low-voltage ride-through, High-voltage ride-through for Italy. Every breakpoint below is read from the code itself, and where a point was taken off a published figure rather than stated in the clause, the section under that chart says so — a boundary the clause states alternative values for.
What is the low-voltage ride-through envelope for Italy (TERNA)?
The plant must ride through for any voltage that stays on or above this envelope. The envelope holds 0 pu from t = 0 to 200 ms; then ramps linearly from 0 pu at 200 ms to 0.85 pu at 2 s; then 0.85 pu from 2 s onward — the last band the envelope defines, with no stated end time.
The chart plots one variant of this boundary — the clause states 2 s / 2,8 s / 4 s. Which value applies depends on the connection; check the clause below against yours. The clause states this boundary as a line; intermediate points are interpolated between its stated vertices.
Applies to Storage plants connecting to the RTN (Terna Allegato A.79)
| From | To | Voltage | Between the points |
|---|---|---|---|
| 0 | 200 ms | 0 pu | Held flat |
| 200 ms | 2 s | 0 → 0.85 pu | Ramps linearly |
| 2 s | no stated end | 0.85 pu | Held flat |
The clause this came from
Terna Allegato A.79 Rev. 00, Marzo 2023, §6.4 'Insensibilità alle variazioni di tensione', Fig. 1 'Caratteristica FRT per Impianti di Accumulo' and Tabella 1 'Parametri FRT' (tA = 200 ms; tB = 2 s / 2,8 s / 4 s); same values in the June 2022 consultation text (Tabella 2). The code defines a linear recovery ramp; the vertices are read from the clause and the chart draws the segment between them.
What is the high-voltage ride-through envelope for Italy (TERNA)?
The plant must ride through for any voltage that stays on or below this envelope. The envelope holds 1.3 pu from t = 0 to 100 ms; then 1.2 pu from 100 ms to 1 s; then 1.15 pu from 1 s onward — the last band the envelope defines, with no stated end time.
The chart plots one variant of this boundary — the clause's footnote reads "1,1 se il punto di connessione è a tensione superiore o uguale 300 kV". Which value applies depends on the connection; check the clause below against yours.
Applies to Storage plants connecting to the RTN (Terna Allegato A.79)
| From | To | Voltage | Between the points |
|---|---|---|---|
| 0 | 100 ms | 1.3 pu | Held flat |
| 100 ms | 1 s | 1.2 pu | Held flat |
| 1 s | no stated end | 1.15 pu | Held flat |
The clause this came from
Terna Allegato A.79 Rev. 00, Marzo 2023, Fig. 1 'Caratteristica FRT per Impianti di Accumulo' (curva OVRT: 1,3 / 1,2 / 1,15 pu with footnote '1,1 se il punto di connessione è a tensione superiore o uguale 300 kV') and Tabella 1 (tC = 100 ms, tD = 1 s).
Operating requirements beyond the envelopes.
The envelopes above are what Italy (TERNA) demands during a disturbance. The rows below are the same regime’s operating and fault-response requirements — reactive capability, frequency response, continuous operating range, ramp rate, RoCoF withstand and fault-current injection — each researched from the document its own row cites, separately from the plotted corpus. Every row carries its clause and a verbatim quote, so you can check it the same way.
| Requirement | What the code states | Clause |
|---|---|---|
| U-Q envelope at rated power Pnd (asymmetric, Type 1 / Type 2) Reactive capability | At rated power Pnd (charging or discharging): underexcited Q at least −0,48 Pnd; overexcited Q at least 0,3 Pnd (Type 1 connections) or 0,4 Pnd (Type 2 connections); total Q range (|overexcited| + |underexcited|) at least 0,96 Pnd; zero reactive exchange at the PdC must be guaranteed for any voltage in 90–110% of nominal. Basis: Pnd = available nominal active power. Binds storage explicitly: Allegato A.79 applies to electrochemical storage plants (Impianti di Accumulo) connected directly to the RTN or indirectly through a network portion above 35 kV — Type 1 = via voltage levels ≥110 kV, Type 2 = 36 kV sections of Gestore (Terna) stations — and additionally to storage plants with efficient power ≥10 MW (§2, PDF p.5). Requirement is defined as a plant-level capability at the Point of Connection (for Type 2 defined on the 36 kV side, §8.3 PDF p.40); horizontal translation of the envelope is allowed to account for internal reactive losses, subject to the quoted floor values. Envelope figures: Fig. 6 (Type 1) and Fig. 8 (Type 2), PDF pp.41–42. | §8.3 Capability di potenza reattiva, first bullet with sub-bullets; Fig. 6 and Fig. 8 |
The clause this row cites§8.3 Capability di potenza reattiva, first bullet with sub-bullets; Fig. 6 and Fig. 8 — “ Quando l'Impianto di Accumulo si trova alla sua potenza nominale (Pnd, in produzione o assorbimento), deve essere in grado di scambiare una potenza reattiva con la rete corrispondente a qualsiasi punto della superficie di inviluppo del profilo U-Q/Pnd riportato in Fig. 6 per gli impianti con connessioni di Tipo 1 e Fig. 8 per gli impianti con connessione di Tipo 2. Al fine di tenere conto delle possibili perdite reattive sulla rete interna, è ammessa la possibilità di traslare orizzontalmente la superficie di inviluppo. Tale traslazione deve comunque assicurare le seguenti prestazioni: in sottoeccitazione deve poter essere fornita una potenza reattiva minima non inferiore a -0,48 Pnd. in sovraeccitazione deve poter essere fornita una potenza reattiva minima non inferiore a 0,3 Pnd per gli impianti con connessione di Tipo 1 e a 0,4 Pnd per gli impianti con connessione di Tipo 2. la somma della potenza reattiva minima fornibile in sovraeccitazione (in valore assoluto) e della potenza reattiva minima fornibile in sottoeccitazione (in valore assoluto) deve essere non inferiore a 0,96 Pnd. deve essere garantito lo scambio reattivo nullo al PdC per qualunque tensione nell'intervallo 90-110% della tensione nominale. ” Translation: “ When the Storage Plant is at its nominal power (Pnd, in production or absorption), it must be able to exchange with the network a reactive power corresponding to any point of the envelope surface of the U-Q/Pnd profile shown in Fig. 6 for plants with Type 1 connections and Fig. 8 for plants with Type 2 connection. In order to account for possible reactive losses on the internal network, horizontal translation of the envelope surface is permitted. Such translation must in any case ensure the following performances: in underexcitation it must be possible to supply a minimum reactive power not lower than −0.48 Pnd. In overexcitation it must be possible to supply a minimum reactive power not lower than 0.3 Pnd for plants with Type 1 connection and 0.4 Pnd for plants with Type 2 connection. The sum of the minimum reactive power deliverable in overexcitation (in absolute value) and the minimum reactive power deliverable in underexcitation (in absolute value) must be not lower than 0.96 Pnd. Zero reactive exchange at the PdC must be guaranteed for any voltage in the 90–110% interval of nominal voltage. ” (Terna, Allegato A.79 al Codice di Rete, Rev. 01, 23 maggio 2025, accessed 2026-08-08) | ||
| Enhanced Q capability at zero active power (P=0) Reactive capability | At zero active power: underexcited Q at least −0,9 Pnd; overexcited Q at least 0,72 Pnd (Type 1) or 0,82 Pnd (Type 2); total Q range at P=0 at least 1,8 Pnd. Basis: Pnd. Binds storage explicitly (same scope as §8.3 generally: Type 1 / Type 2 RTN-connected storage plants and storage ≥10 MW efficient power). Applies when the active-power exchange at the point of connection is below Pnd in absolute value: reactive exchange must then be limited only by the individual inverters' reactive limits, with the resulting P-Q curve per Fig. 7 (Type 1) / Fig. 9 (Type 2), PDF pp.41–42; the quoted floor values apply after any horizontal translation of the envelope. | §8.3 Capability di potenza reattiva, second bullet with sub-bullets; Fig. 7 and Fig. 9 |
The clause this row cites§8.3 Capability di potenza reattiva, second bullet with sub-bullets; Fig. 7 and Fig. 9 — “ in sottoeccitazione, a potenza attiva nulla, deve poter essere fornita una potenza reattiva non inferiore a -0,9 Pnd. in sovraeccitazione, a potenza attiva nulla, deve poter essere fornita una potenza reattiva non inferiore a 0,72 Pnd per il Tipo 1 e 0,82 Pnd per il Tipo 2. a potenza attiva nulla, la somma della potenza reattiva minima fornibile in sovraeccitazione (in valore assoluto) e della potenza reattiva minima fornibile in sottoeccitazione (in valore assoluto) deve essere non inferiore a 1,8 Pnd. ” Translation: “ In underexcitation, at zero active power, it must be possible to supply a reactive power not lower than −0.9 Pnd. In overexcitation, at zero active power, it must be possible to supply a reactive power not lower than 0.72 Pnd for Type 1 and 0.82 Pnd for Type 2. At zero active power, the sum of the minimum reactive power deliverable in overexcitation (in absolute value) and the minimum reactive power deliverable in underexcitation (in absolute value) must be not lower than 1.8 Pnd. ” (Terna, Allegato A.79 al Codice di Rete, Rev. 01, 23 maggio 2025, accessed 2026-08-08) | ||
| FSM droop formula, adjustable regulation bands and deadband Frequency response | FSM droop set via σ_FSMu = (50 − fB1)/50/B_FSMu and σ_FSMo = (fB2 − 50)/50/B_FSMo; regulation semi-bands B_FSMu and B_FSMo each settable 0–100% of Pn (default 10,0% Pn); deadband ΔfDB1 = ΔfDB2 settable 0 to ±0,5 Hz in 0,001 Hz steps, default ±0,01 Hz; default thresholds fB1 = 49,8 Hz, fB2 = 50,2 Hz. Basis: Pn = nominal power of the storage plant. Binds storage explicitly: 'L'implementazione della regolazione FSM è obbligatoria per tutti gli Impianti di Accumulo di cui al par. 2' (§8.5.2, PDF p.51). §8.5.2 (PDF p.51) additionally requires the FSM deadband ΔfDB to be settable in the interval [0;500 mHz] per Gestore instructions, consistent with the Tabella 5 range quoted below. Rev. 01 adds a lead-lag block on the FSM/LFSM primary-regulation output (Fig. 13, PDF p.50; T1 settable 0–100 s, T2 0,1–10 s, excluded by default T1=0, T2=0); per ARERA Delibera 209/2025/R/eel point 3 the lead-lag functionality is obligatory for electrochemical storage systems entering service after the new Code version's entry into force (23 May 2025). | §8.5.2 Regolazione FSM + §8.5.5 Campi di regolazione, Tabella 5 — Parametri di taratura FSM/LFSM (table transcription) |
The clauses this row cites§8.5.2 Regolazione FSM — “ Il coefficiente di proporzionalità dovrà essere imposto in modo tale per cui si ottenga uno statismo dell'Impianto di Accumulo pari a: σFSMu = (50 -fB1) / 50 / BFSMu per variazioni di frequenza nel range [fB1 … 50 Hz]; σFSMo = (fB2-50) / 50 / BFSMo per variazioni di frequenza nel range [50 Hz … fB2]. Le due semi-bande di regolazione BFSMu e BFSMo, rispettivamente in sotto e sovra-frequenza, dovranno essere parametri tarabili distintamente nel range 0%÷100% del valore della potenza nominale dell'Impianto di Accumulo. ” Translation: “ The proportionality coefficient shall be imposed such that a droop of the Storage Plant is obtained equal to: σFSMu = (50 − fB1) / 50 / BFSMu for frequency variations in the range [fB1 … 50 Hz]; σFSMo = (fB2 − 50) / 50 / BFSMo for frequency variations in the range [50 Hz … fB2]. The two regulation semi-bands BFSMu and BFSMo, respectively in under- and over-frequency, shall be parameters settable separately in the range 0%–100% of the nominal power value of the Storage Plant. ” (Terna, Allegato A.79 al Codice di Rete, Rev. 01, 23 maggio 2025, accessed 2026-08-08) §8.5.5 Campi di regolazione, Tabella 5 — Parametri di taratura FSM/LFSM (table transcription) — “ A | fA [Hz] | 47,5 ÷ 50,0 | 0,001 | 49,5 — B1 | fB1 [Hz] | 49,5 ÷ 50,0 | 0,001 | 49,8 — B2 | fB2 [Hz] | 50,0 ÷ 50,5 | 0,001 | 50,2 — Banda morta DB1 - DB2 | ΔfDB1 = ΔfDB2 [Hz] | 0 ÷ ±0,5 | 0,001 | ±0,01 — C | fC [Hz] | 50,2 ÷ 51,5 | 0,001 | 51,5 — BFSM-O | [% Pn] | 0 ÷ 100 | 0,1 | 10,0 — BFSM-U | [% Pn] | 0 ÷ 100 | 0,1 | 10,0 ” Translation: “ A | fA [Hz] | 47,5 ÷ 50,0 | 0,001 | 49,5 — B1 | fB1 [Hz] | 49,5 ÷ 50,0 | 0,001 | 49,8 — B2 | fB2 [Hz] | 50,0 ÷ 50,5 | 0,001 | 50,2 — Dead band DB1 - DB2 | ΔfDB1 = ΔfDB2 [Hz] | 0 ÷ ±0,5 | 0,001 | ±0,01 — C | fC [Hz] | 50,2 ÷ 51,5 | 0,001 | 51,5 — BFSM-O | [% Pn] | 0 ÷ 100 | 0,1 | 10,0 — BFSM-U | [% Pn] | 0 ÷ 100 | 0,1 | 10,0 ” (Terna, Allegato A.79 al Codice di Rete, Rev. 01, 23 maggio 2025, accessed 2026-08-08) | ||
| LFSM-U / LFSM-O: activation and unlimited sustain to full SoC exhaustion Frequency response | LFSM-U activates below threshold fB1 (default 49,8 Hz) and may deploy the full remaining upward margin MU = Psmax − Pfn, reaching maximum discharge power at fA (default 49,5 Hz); if the frequency error so requires ('Qualora l'errore di frequenza lo richieda'), the LFSM-U contribution must be supplied without time or energy limitation, until complete exhaustion of the plant's energy capacity. Symmetrically, LFSM-O activates above fB2 (default 50,2 Hz) down to maximum charging power at fC (default 51,5 Hz), when required ('Quando richiesto'), without time or energy limitation until the storage is completely full (§8.5.4). Binds storage explicitly: 'Tutti gli impianti di accumulo devono fornire un supporto al SEN...' (all storage plants within the Allegato's scope, §2). Defined at the point of connection, additive to the current operating point per the P(f) curve of Fig. 12 (PDF p.49). Threshold defaults from Tabella 5, §8.5.5 (PDF p.54), quoted in the FSM claim. The LFSM-O sustain clause (PDF p.54) mirrors the quoted LFSM-U one: 'senza limitazione di tempo o energia e fino al completo riempimento della capacità energetica dell'Impianto di Accumulo'. | §8.5.3 Regolazione in sottofrequenza (LFSM-U); §8.5.4 Regolazione in sovra-frequenza (LFSM-O) + §8.5.3, closing paragraph (sustain requirement) |
The clauses this row cites§8.5.3 Regolazione in sottofrequenza (LFSM-U); §8.5.4 Regolazione in sovra-frequenza (LFSM-O) — “ Tutti gli impianti di accumulo devono fornire un supporto al SEN nei casi di eventi di rete che provocano grandi transitori di sotto-frequenza; tale supporto è denominato regolazione LFSM-U (Limited Frequency Sensitive Mode - Under-Frequency) e consiste, quando la frequenza scende al di sotto di una determinata soglia di sotto-frequenza (fB1), nel modificare automaticamente la potenza attiva scambiata con la rete nel punto di connessione in coerenza con la curva di Fig. 12. Se richiesto dall'errore di frequenza, potrà essere erogato tutto il margine in incremento ancora disponibile MU= Psmax-Pfn fino a raggiungere la potenza di scarica massima a fA. ” Translation: “ All storage plants must provide support to the SEN [national electricity system] in cases of network events causing large under-frequency transients; this support is called LFSM-U regulation (Limited Frequency Sensitive Mode - Under-Frequency) and consists, when the frequency falls below a given under-frequency threshold (fB1), in automatically modifying the active power exchanged with the network at the point of connection consistently with the curve of Fig. 12. If required by the frequency error, the entire still-available incremental margin MU = Psmax − Pfn may be delivered, up to reaching the maximum discharge power at fA. ” (Terna, Allegato A.79 al Codice di Rete, Rev. 01, 23 maggio 2025, accessed 2026-08-08) §8.5.3, closing paragraph (sustain requirement) — “ Qualora l'errore di frequenza lo richieda, il contributo della regolazione LFSM-U deve essere fornito senza limitazione di tempo o energia e fino al completo esaurimento della capacità energetica dell'Impianto di Accumulo. ” Translation: “ Where the frequency error so requires, the contribution of the LFSM-U regulation must be provided without limitation of time or energy and until the complete exhaustion of the energy capacity of the Impianto di Accumulo [Storage Plant]. ” (Terna, Allegato A.79 al Codice di Rete, Rev. 01, 23 maggio 2025, accessed 2026-08-08) | ||
| Continuous voltage band (85–115% / 85–110% Vn) and frequency band (47,5–51,5 Hz) Continuous operating range | Unlimited-time operation at any P/Q value for: 85%Vn ≤ V ≤ 115%Vn where the connection point is below 300 kV, and 85%Vn ≤ V ≤ 110%Vn at or above 300 kV (Type 1 connections; Type 2 sees the same range on the transformer primary side). Frequency: unlimited-time connection for 47,5 Hz ≤ f ≤ 51,5 Hz; connection for limited times below 47,5 Hz and above 51,5 Hz (durations not quantified in A.79 — plant limits are declared to the Gestore; stated in §6.2, document p. 15, but not carried in the quoted text). Binds storage explicitly (Impianti di Accumulo, §6.2 within scope of §2). Voltage bands are defined at the point of connection; for Type 2 connections the AT-AAT/36 kV transformer on-load tap changer is managed to keep the delivery-point voltage near nominal while allowing the same range on the primary side. For frequencies outside 47,5–51,5 Hz the code requires limited-time connection but states no minimum durations; the owner must not voluntarily limit the plant's operating range and must declare its limits to the Gestore. | §6.2 Limiti di funzionamento + §6.2 Limiti di funzionamento, 'Per tutti i tipi di connessione' (frequency interval) |
The clauses this row cites§6.2 Limiti di funzionamento — “ Essi devono essere in grado di restare connessi alla rete e funzionare per un tempo indefinito per tutti i valori di potenza attiva e reattiva quando la tensione nel punto di connessione si trova nei seguenti intervalli: Connessioni di Tipo 1: 85%Vn ≤ V ≤ 115%Vn se il punto di connessione è a tensione inferiore a 300kV 85%Vn ≤ V ≤ 110%Vn se il punto di connessione è a tensione superiore o uguale 300kV ” Translation: “ They must be able to remain connected to the network and operate for an indefinite time for all active and reactive power values when the voltage at the point of connection lies in the following intervals: Type 1 connections: 85%Vn ≤ V ≤ 115%Vn if the point of connection is at a voltage below 300 kV; 85%Vn ≤ V ≤ 110%Vn if the point of connection is at a voltage above or equal to 300 kV. ” (Terna, Allegato A.79 al Codice di Rete, Rev. 01, 23 maggio 2025, accessed 2026-08-08) §6.2 Limiti di funzionamento, 'Per tutti i tipi di connessione' (frequency interval) — “ Riguardo all'esercizio in parallelo con la rete AT in funzione della frequenza, l'Impianto di Accumulo deve rimanere connesso alla rete per un tempo indefinito, per valori di frequenza compresi nel seguente intervallo: 47,5 Hz ≤ f ≤ 51,5 Hz e devono rimanere connessi alla rete per tempi limitati quando la frequenza si trova al di sotto di 47,5 Hz e al di sopra 51,5 Hz. ” Translation: “ Regarding parallel operation with the HV network as a function of frequency, the Storage Plant must remain connected to the network for an indefinite time for frequency values within the following interval: 47,5 Hz ≤ f ≤ 51,5 Hz — and they must remain connected to the network for limited times when the frequency is below 47,5 Hz or above 51,5 Hz. ” (Terna, Allegato A.79 al Codice di Rete, Rev. 01, 23 maggio 2025, accessed 2026-08-08) | ||
| Active-power ramp limit — agreed with Terna, typically 1–200%/min of Pn Ramp rate | The maximum load-variation (ramp) rate must be agreed with the Gestore, typically in the range 1÷200% per minute of the plant's nominal power Pn; wider intervals can be agreed on request. Ramp limiting must be continuous and linear, and a different gradient must be assignable for each type of active-power variation (e.g. secondary regulation, tertiary regulation, scheduled variation). Basis: Pn. Note: 'tipicamente' — the 1–200%/min range is indicative, not a fixed limit. Binds storage explicitly (Impianto di Accumulo, §8.1.1 within scope of §2). The plant must be able to follow setpoint/programme variations with its maximum capability; the ramp limitation applies to the charge/discharge setpoint rate of change when required, and generally does not apply when the variation is explicitly requested by the Gestore. The per-variation-type gradient requirement and the exemption for variations explicitly requested by the Gestore are stated in §8.1.1 (document p. 37) but are not carried in the quoted text. | §8.1.1 Limiti di rampa |
The clause this row cites§8.1.1 Limiti di rampa — “ L'Impianto di Accumulo deve essere in grado di seguire le variazioni dei setpoint e del programma con le massime prestazioni di cui è in grado; deve comunque essere predisposto in modo tale da poter limitare se richiesto, la velocità di variazione del set-point di carico, e conseguentemente della potenza, in maniera continua e lineare. Il valore della massima velocità di variazione del carico deve essere concordato con il Gestore, tipicamente nel range 1÷200%/minuto della potenza nominale dell'Impianto di Accumulo (Pn); su richiesta il Gestore può concordare intervalli più ampi. ” Translation: “ The Storage Plant must be able to follow setpoint and programme variations with the maximum performance it is capable of; it must in any case be arranged so as to be able to limit, if required, the rate of change of the load set-point, and consequently of the power, in a continuous and linear manner. The value of the maximum load-variation rate must be agreed with the Gestore [system operator], typically in the range 1÷200%/minute of the nominal power of the Storage Plant (Pn); on request the Gestore may agree wider intervals. ” (Terna, Allegato A.79 al Codice di Rete, Rev. 01, 23 maggio 2025, accessed 2026-08-08) | ||
| ROCOF immunity 2,5 Hz/s (measured over ≥5 cycles / 100 ms) RoCoF withstand | Storage plants must remain connected and operate for rate-of-change-of-frequency values up to 2,5 Hz/s, with the derivative calculated over at least 5 cycles (100 ms); the calculation window must be settable between 100 ms and 1 s. RoCoF protections limiting wider capability are not permitted. Binds storage explicitly (Impianto di Accumulo, §6.3 within scope of §2: Type 1 and Type 2 RTN-connected storage and storage ≥10 MW efficient power). Withstand requirement, not an injection requirement. | §6.3 Resistenza alla derivata di frequenza |
The clause this row cites§6.3 Resistenza alla derivata di frequenza — “ Un Impianto di Accumulo deve essere in grado di restare connesso alla rete e di funzionare con valori di derivata di frequenza fino a 2,5 Hz/s. La derivata di frequenza deve essere calcolata su un numero di cicli pari ad almeno 5 (100 ms). Il calcolo della derivata deve poter essere effettuato con una finestra variabile impostabile tra 100ms e 1s (la finestra variabile viene utilizzata in coerenza al valore della derivata da calcolare, generalmente crescente al diminuire del valore della derivata). Non è consentita l'installazione di protezioni RoCoF che limitino a tali valori eventuali prestazioni più ampie in derivata di frequenza. ” Translation: “ A Storage Plant must be able to remain connected to the network and to operate with frequency-derivative values up to 2.5 Hz/s. The frequency derivative must be calculated over a number of cycles equal to at least 5 (100 ms). The calculation of the derivative must be performable with a variable window settable between 100 ms and 1 s (the variable window is used consistently with the derivative value to be calculated, generally increasing as the derivative value decreases). The installation of RoCoF protections that would limit to such values any wider frequency-derivative capability is not permitted. ” (Terna, Allegato A.79 al Codice di Rete, Rev. 01, 23 maggio 2025, accessed 2026-08-08) | ||
| Fault reactive-current injection: ΔIq = K·ΔVd, K settable 0–5 (default 2) Fault-current injection | During faults the plant must inject positive-sequence reactive current proportional to the positive-sequence voltage deviation: ΔIq = KLV·(VSLV − Vd) for Vd < VSLV, ΔIq = 0 inside the deadband VSLV ≤ Vd ≤ VSHV, ΔIq = KHV·(VSHV − Vd) for Vd > VSHV, with ΔIq in p.u. of plant nominal current and ΔVd in p.u. of nominal voltage. KLV and KHV settable in range 0÷5, default 2. Activation deadband settable: VSLV = 0,85÷0,60 Vn (default 0,85 Vn), VSHV = 1,10÷1,15 Vn (default 1,10 Vn). Voltage measured at the inverter terminals. Binds storage explicitly; the voltage-support function is enabled on Gestore request (Appendice B, opening; §8.10 PDF p.59). Reactive priority: 'Data la priorità assegnata alla regolazione della potenza reattiva, la potenza attiva erogata diviene funzione della corrente reattiva richiesta e dei limiti impostati' (point 6, PDF p.80). Response time: inverters must supply the requested reactive current within 50 ms of the voltage entering the delivery band (point 5, PDF p.80: 'Gli inverter devono essere in grado di fornire la corrente reattiva richiesta entro un tempo di 50 ms a partire dall'ingresso della tensione nella fascia di erogazione (tempo di risposta).'). Below 20% Vn the maximum available reactive current must be injected; injection is not required below a manufacturer-defined threshold not exceeding 10% Vn (point 3, PDF p.80). Current angle settable in minimum interval [30°;80°], default 80° (PDF p.79). Negative sequence: for dissymmetric faults Rev. 01 accepts solutions injecting positive- and negative-sequence current simultaneously with separately declared parameters; by default the support function must be excludable or limitable to symmetrical faults only (PDF p.80). The VSLV/VSHV deadband setting ranges and the inverter-terminal measurement point are stated in Appendice B (document pp. 79-80) but are not carried in the quoted text. | Appendice B — Supporto alla tensione durante i guasti in rete, point 2 + Appendice B, point 2 (continuation) |
The clauses this row citesAppendice B — Supporto alla tensione durante i guasti in rete, point 2 — “ La corrente reattiva di sequenza diretta prodotta dall'Impianto di Accumulo ΔIq (espressa in p.u. della corrente nominale dell'Impianto di Accumulo) deve essere proporzionale alla variazione di tensione diretta ΔVd (espressa in p.u. della tensione nominale) secondo un coefficiente di proporzionalità K regolabile e diverso per le condizioni di UVRT e OVRT: se Vd < VSLV ΔIq = KLV (VSLV -Vd) se VSLV ≤ Vd ≤ VSHV ΔIq = 0 se Vd > VSHV ΔIq = KHV (VSHV -Vd) ” Translation: “ The positive-sequence reactive current produced by the Storage Plant ΔIq (expressed in p.u. of the nominal current of the Storage Plant) must be proportional to the positive-sequence voltage variation ΔVd (expressed in p.u. of nominal voltage) according to an adjustable proportionality coefficient K, different for UVRT and OVRT conditions: if Vd < VSLV, ΔIq = KLV (VSLV − Vd); if VSLV ≤ Vd ≤ VSHV, ΔIq = 0; if Vd > VSHV, ΔIq = KHV (VSHV − Vd). ” (Terna, Allegato A.79 al Codice di Rete, Rev. 01, 23 maggio 2025, accessed 2026-08-08) Appendice B, point 2 (continuation) — “ Il campo di regolazione richiesto per i due coefficienti di proporzionalità KLV e KHV è il seguente: 0 ÷ 5. Valori di default: 2. ” Translation: “ The required adjustment range for the two proportionality coefficients KLV and KHV is the following: 0 ÷ 5. Default values: 2. ” (Terna, Allegato A.79 al Codice di Rete, Rev. 01, 23 maggio 2025, accessed 2026-08-08) | ||
Who does Italy (TERNA) bind, and since when?
Storage plants connecting to the RTN (Terna Allegato A.79). No date of effect is published here — grid codes are reissued, so check the current issue before relying on it.
These figures are a reading aid, not legal advice. Grid codes are reissued: verify against the current edition before you design to them.
Curve data last checked against the code on — 66 standards, 130 envelopes, published by bess.engineer under CC BY 4.0.
Questions this page answers about Italy (TERNA)
- Does Italy (TERNA) require ride-through, or only that the plant does not trip?
- Ride-through. Every envelope on this page is a performance duty the plant must meet, not a protection-setting no-trip boundary — they are different obligations. That is what these curves are; they are not everything Italy (TERNA) contains. The requirement sentence under each chart says which side of the curve is the compliant one.
- Are the numbers on this page taken from Italy (TERNA) itself?
- Every breakpoint is read from the code, and where a point was taken off a published figure rather than stated in the clause, the section under that chart says so — on this page that includes a boundary the clause states alternative values for. The clause each curve came from is quoted under it.
- Which events are charted for Italy (TERNA)?
- Italy (TERNA) is charted here with 2 envelopes — low-voltage ride-through, high-voltage ride-through (LVRT, HVRT). No frequency envelope is charted here — check Italy (TERNA) itself before concluding it sets none.
Ride-through, in context.
An envelope is a compliance boundary; understanding why it exists is a different question. The ride-through and grid-forming entries cover the engineering, and the Engineering Foundations course builds it from the physics up.
Elsewhere in Europe: Ireland (EirGrid), Netherlands (TenneT), Norway (Statnett NVF 2025), Poland (PSE Wymogi 2025), Romania (Transelectrica/ANRE storage norm), Spain (P.O. 12.3), and 13 more