# Wind Turbine Predictive Fault Diagnostics Based on a Novel Long Short-Term Memory Model
## 5 Discussion
### Confusion Matrix  
T2V-LSTM is the best-performing classifier for both overall fault predictions and specific fault predictions. Then, an additive classification step is to visualise the predictions of 10 min, 30 min, 1 h, 2 h, and 3 h in advance via the confusion matrices under T2V-LSTM in Figure 13. The fault-free and fault cases in Figure 13 are represented by their corresponding event codes in Table 3.  
Except for more FNs than FPs from PcsTrip (event code 701) and pitch fatal faults (event code 435), the balances between recall and precision scores are established with regard to their unbiased FPs and FNs from confusion matrices in Figure 13.  
Figure 13: Confusion matrices under T2V-LSTM at five timestamps: (**a**) \(t-1\) (10 min); (**b**) \(t-3\) (30 min); (**c**) \(t-6\) (1 h); (**d**) \(t-12\) (2 h); (**e**) \(t-18\) (3 h).  
The most frequent (Demoted) gearbox pressure 2 faults (event code 570) witness successful fault predictions with few FNs but obtain the 14 FPs at \(t-12\) from Figure 13d. More accurate predictions can be witnessed on the Blade 3 slow response (event code 399) by yielding, at most, 1 FN or FP. Gearbox cooling pressure faults (event code 543) have great fault-free predictions due to minor FPs, but the relevant misdiagnosed fault cases increasing with time, 6 and 9 FNs at timestamps \(t-12\) and \(t-18\), as seen in Figure 13d,e, respectively.  
Sub-pitch fatal faults (event code 1219) have TPs ranging from 161 to 168, with a maximum of 7 FPs, resulting in MIPs over 95%. Since the fewest TPs are obtained at \(t-18\) in Figure 13e with 16 misdiagnosed fault cases, the minimum MIR reaches 90.96%.  
HPU 2 pump active faults (event code 290) obtain the best prediction at \(t-3\) with the maximum 102 TPs, 9 FNs, and a total of 21 FPs, so the resultant MIP and MIR reach 82.92% and 91.89%, respectively. However, the worst prediction at \(t-18\) is yielded with a minimum of 85 TPs, 26 FNs, and 29 FPs in total, leading to the poorest MIP (74.56%) and MIR (76.57%). Hence, the predictions on HPU 2 pump active faults witness less success over a longer prediction horizon.  
In addition to the HPU 2 pump active faults, the prediction scores on the least frequent PcsOff faults (event code 700) gradually worsen over time. The best prediction on PcsOff is at \(t-3\), when only 1 FN and 2 FPs are obtained to confirm its notable MIP (95.74%) and MIR (97.82%). However, the worst prediction at \(t-18\) generates 38 TPs with a total of 6 FPs and 8 FNs, thereby yielding the resultant MIP (86.36%) and MIR (82.60%).  
Regarding PcsTrip faults (event code 701), MIPs are always satisfactory concerning the maximum 7 FPs at \(t-6\), whilst MIPs decline over time. The best prediction on PcsTrip faults at \(t-3\) is provided with 72 TPs, 6 FPs, and 9 FNs, leading to the resultant MIP (92.30%) and MIR (88.88%). By comparison, the worst case at \(t-18\) yields relatively poorer results with 61 TPs, 4 FPs, and 20 FNs, leading to an agreeable MIP (93.84%) but an undervalued MIR (75.30%). Hence, the pre24 dictions on PcsTrip have excellent precision scores, but the resulting F-scores are brought down by gradually declined MIRs.  
In addition to PcsTrip faults, the subsequent F-scores of pitch fatal faults (event code 435) are declined by poorer recall scores. Among all faults, the pitch fatal faults witness the most misdiagnosed fault cases, yielding the maximum FNs throughout the time. Initially, at \(t-1\), the MIR (69.48%) is acceptable due to 107 TPs out of 154 total fault cases, whilst the MIP (79.85%) is much greater owing to a total of 27 FPs. With a longer prediction horizon, more fault cases are wrongly predicted, accompanied by reduced TPs and increased FNs, which are shown in Figure 12. It is considerable that the prediction at \(t-18\) yields an MIR of merely 49.35%, along with its relevant MIP scoring 72.38%. Hence, pitch fatal faults have observed extremely lower MIRs in comparison to other faults, and their recall scores are exceptionally exceeded by the relevant precision scores.