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The SMV Max Delay parameter, found via menu path Configuration > System, defines how long the receiver waits for the SMV frames before activating the TxTR ALARM output. This setting also delays the local measurements of the receiver to keep them correctly time aligned. The SMV Max Delay values include sampling, processing and network delay.

Warning: For best performance, the SMV Max Delay value should not be set needlessly high since this delays the protection by an equal amount of time. Setting it too low can cause SMV samples to arrive after the set deadline and thus make SMV-based protection inoperable. To determine suitable SMV Max Delay values, see the tables below.

TxTR ALARM activates when two or more consecutive SMV frames are lost or late. A single loss of frame is corrected with a zero-order hold scheme. The effect on protection is considered negligible in this case and it does not activate the TxTR WARNING or ALARM outputs.

Table 1. 9-2 max delay settings
61869-9
Number of hops in network	Internal application delay (ms) ¹	Internal switch latency (ms) ²	Store and forward latency (ms) ²	Queue latency (ms) ^2,³	Additional tolerance (ms) ⁴	Theoretical max delay (ms)	Recommended max delay setting
2	1,62	0,02	0,024	0,24	0,08	1,98	low
5	1,62	0,05	0,06	0,6	0,2	2,53	low
10	1,62	0,1	0,12	1,2	0,25	3,29	medium
15	1,62	0,15	0,18	1,8	0,3	4,05	high
20	1,62	0,2	0,24	2,4	0,35	4,81	high
25	1,62	0,25	0,3	3	0,4	5,57	maximum
30	1,62	0,3	0,36	3,6	0,45	6,33	maximum

Table 2. 9-2LE Max delay settings
92LE
Number of hops in network	Internal application delay (ms)		Internal switch latency (ms) ²	Store and forward latency (ms) ²	Queue latency (ms) ^{2, 3}	Additional tolerance (ms) ⁴	Theoretical max delay (ms)		Recommended max delay setting
	50 Hz ¹	60 Hz					50 Hz	60 Hz	50 Hz	60 Hz
2	1,61	1,38	0,02	0,024	0,24	0,08	1,97	1,75	low	low
5	1,61	1,38	0,05	0,06	0,6	0,2	2,52	2,29	low	low
10	1,61	1,38	0,1	0,12	1,2	0,25	3,28	3,05	medium	medium
15	1,61	1,38	0,15	0,18	1,8	0,3	4,04	3,81	medium	high
20	1,61	1,38	0,2	0,24	2,4	0,35	4,8	4,57	high	high
25	1,61	1,38	0,25	0,3	3	0,4	5,56	5,33	maximum	maximum
30	1,61	1,38	0,3	0,36	3,6	0,45	6,32	6,09	maximum	maximum

Table 3. Meaning of SMV Max delay enumerator value in time (ms)
SMV Max delay in [ms]
Enumerator value	9-2LE 50 Hz	61869-9 50 Hz	9-2LE 60 Hz	61869-9 60 Hz
minimum	1,72	1,68	1,45	1,66
low	2,97	2,73	2,49	2,7
medium	4,22	3,77	3,53	3,74
high	5,47	4,81	4,58	4,78
maximum	6,72	5,85	5,62	5,83

The differentiator between 9-2LE and 61869-9 is the number of ASDU, which determines which column is active (9-2LE with 1 ASDU and 61869-9 with 2 ASDU).

50 or 60 Hz comes from IED rated frequency setting in LLN0.

Table 4. Protection latencies
MV max delay enum setting	Protection delay (ms)
	9-2LE 50 Hz	61869-9 50 Hz	9-2LE 60 Hz	61869-9 60 Hz
minimum	0,31	0,31	0,35	0,52
low	1,35	1,56	1,39	1,56
medium	2,4	2,81	2,43	2,6
high	3,44	4,06	3,47	3,65
maximum	4,48	5,31	4,51	4,69

¹ Includes delay of 0,208 ms due to 2 ASDU in SMV frame

² Latencies are totals over the number of hops and they are calculated for 100 Mbit full-duplex Ethernet network.

³ Queue latency calculated when the port has started to send a full-sized frame (1500 bytes) before the SMV frame and the switch has been configured to prioritize SMV

⁴ Additional tolerance in case of long wires or disturbance in network